This guide will explain everything I know about FSX including tweaks, settings, addons etc...
How to prepare your PC, and install FSX:
The preperation of your PC, and a proper installation of FSX are vital to have the hardest 3d application in the world run to the best capability of your hardware. First, I reccomend following NickN's guide to preparing your PC for FSX. Once your PC is all clean and savvy, it's time to install FSX (I highly reccomend having Acceleration with your original copy [not required]), first install the original copy of FSX, then run FSX to make sure it just runs. Then restart your PC and install Acceleration or SP1 and SP2 in that order (only if you do not have Acceleration...Acceleration includes both SPs). Again, run it to make sure it runs (if it doesn't, I posted several helpfull forums below). Now that everything is installed you will have the main FSX folder (where ever you installed it, IE: program files), a folder for your logbook and settings in desktop//documents, and another folder in desktop//AppData/microsoft/FSX which includes the FSX.cfg file and some others (NOTE: if you don't see the AppData folder, go to folder option, go to the view tab and toggle/check view hidden folders)
Great, your about ready, now for the fun stuff.
First, FSX is VERY CPU dependent, it can suck the performence of an I7 CPU like a black hole hungry for a star. And yeah, you need a good graphics card to run it, but all you need is a ATI 3850, or a Nvidia 8800gt. Anything more and you will not see much of a performence boost...also, SLI and Cross fire are both totally useless in FSX, for proof check out this benchmark (also usefull for all modern GPUs in FSX).
So, what can we do about it? Well, throught the MSFSX community, many people have come out with tweaks that configure the FSX.cfg to enhance FPS...and it actually works, I'll post a couple of links, and I'll go through the basics.
Okay, so I'll repeat the basic ones. (NOTE: Before you do this I reccomend you make a vanilla copy of the original FSX.cfg file [and if you skipped to this point, the cfg file is in desktop//AppData/roaming/microsoft/fsx])
Add [BufferPools] at the end of a section (NOTE: the  indicate a new section within the file), then add PoolSize=5000000... Okay so the number basicly has a relationship to the Vram, and this tweak helps with the FPS spikes when turning in flight, or panning. I use 8000000 because I have a 512mb card, if you have a 256mb 5000000 is a good number, and if you have more than 512mb it's a good idea to have the number inbetween 10000000-15000000 (these numbers are in the millions, default is 4million)
Next, If you look in the [Display] section, you should see TEXTURE_BANDWIDTH_MULT=30, switch that number to 70-80,it should increase FPS.
Also in the [Display] section, you should see WideViewAspect=False, set to true if you have a widescreen monitor.
Okay, that's a few of the good ones. I also reccomend that you OC your CPU and GPU if you feel up to it, but please read some guides before you do that. (google them)
The dreaded Settings:
Okay, now that our FSX's are all nice and tweaked, it's time to setup our options. Before we do this though, we need to go over drivers. I haven't used a nvidia card in 6 years so I'm going to stick with the Catalyst control center layout, but you Nvidia guys pay attention as well. Okay, we want to make a 3d profile application for FSX. I reccomend these settings to start with, 4x(or 8xAA)(Edge-detect), AFx16, Catalyst A.I (advanced), Minimap detal level (quality) [this is for the in-game text, so it doesn't get blurry],Wait for vertical refresh (always on), Adaptive AA set to performence, Triple buffering on.
Now, to the actual FSX settings. In the settings tab, below the slider's box, you will see a Customize button, click it. Alright, Target frame is a very usefull tool in FSX, you can set it low to 20, or have it at unlimited...in various cases theres advantages to both. If you keep the FPS locked low, it lets your CPU prepare more things (like AI, weather, etc...) and this keeps your FPS steady, On the other hand, putting it on unlimited will give you a 5-15 FPS increase in citys or other buisy areas. However, if you have it at unlimited, it could spike in alot of places (like mountain or plain areas), making you feel like a real world pilot on a red bull downer. I keep my FPS locked at unlimited. Also, it is reccomended to turn cockpit tool tips and aircraft labels off to reduce stutters.
Now for resolution this is obviously up to your preference, the higher the better.
Below, there's 3 texture filterings: Blinear, Trilinear and Antiscroptic...and the quality is based in that order, I highly reccomend using Trilinear. (NOTE: you can always turn on AF in your driver software with Tri. or Bli.)
KEEP AA HERE OFF!! (use driver AA)
To the upper right, you will see a slider called Global Texture Resolution. It has a light impact on the game, thus I reccomend everyone keeps it at very high! (no exceptions!)
Below, there are four boxes: Preview Dx10, Lens flare, Light bloom and advanced animations. Dx10 is completely buggy, so keep it off. Lens flare and Light bloom are extra little nice things that can take away 5-10fps, and advanced animations display wings bending and other realistic stuff with no drawback on performence. The informational text have no bearing on performence.
To the aircraft tab... choose your prefered default cockpit 3d or 2d... I would reccomend enabling the high resolution 3d cockpit if your a virtual cockpit guy, and I'd recommend sliding the 2d-transperence up if your a 2d cockpit guy.The exterior settings include: Aircraft cast shadows on ground which is very usefull for landings, with only a 2fps drawback, Aircraft cast shadows onself is pretty absent, so I'd keep it off. Finely,the aircraft lights illuminate ground is realistic for night flights, I keep it on.
Next, is the scary scenery tab where I have spent countless hours tweaking the sliders. The level of detail radius is simply that...I have used small (2.5mi radius), medium (3.5mi radius), and large (4.5 mi radius)... Large is reccomended for most systems, but don't forget it's okay to set it lower. Mesh complexity defines the trees, bushes and little stuff like that...if you fly in the mountains I reccomend keeping that in the 80-100% area, and if you fly over a flat area turn it below 25% (NOTE: The mesh slider does have a small impact on FPS, but alot of trees visible when flying over mountains adds alot of depth). Mesh resolution sharpens the mesh (reccomend everyone sets it at 10m)...so same case as before, if you like trees raise the slider (Note: this doesn't have as much impact as the complexity, so feel free to turn it up).Texture resolution modifies buildings and the ground. Again, having this high doesn't hurt performence to much (I reccomend putting this all the way up to 7cm, it makes a big visual diffrence). Now, in my opinion one of the most valueble sliders...Water effects, when it's turned high the water in FSX looks spectacular, but it has a big drain on performence. So if you need to cut back, take it to the x1 area, but if you can afford to look at some pretty fine water, having it at high x2, max x2 is quiet a treat (I reccomend you use low x2, it looks good with a insignificant perf hit). The Land detail textures box modifys the buildings, mesh and eveything on the ground, keep it on unless you have FPS problems. The Scenery complexity slider modifies custom buildings in citys and airports. Going at and above very dense means terrible FPS in citys and big airports no matter how good your rig is, I reccomend keeping it at dense. The Autogen slider creates small buildings around citys, metropolitan areas, rural areas...and everywhere... I reccomend keeping it at very dense or higher if your system can handle it (NOTE: if sparse is to much for your PC, there are tweaks to make it more like FS9).The ground scenery shadows box is usless in my opinion, keep it off. Finely, the special effects detail slider modifys actions like waves, fireworks and other weard stuff in a flight sim, I reccomend keeping it at high since no fps hit is noticed.
Now to weather. Cloud draw distence modifies how far away from your position clouds are rendered, this has a small impact on performence, I keep mine at above 80mi. Thermal Visualization is usefull for glider pilots, but it takes a fps downer, toggle it off if your not going to fly gliders. Simple clouds renders clouds like they did in fs8 and fs9...boaring... I use detailed clouds that look more volumetric, and the slider modifies complexity, again, the higher the worse fps.
Finely, we have traffic, and all of it takes a toll on our CPUs. Setting airline traffic above 60% is a death wish in big citys and airports, keep it below that. Alot of FPS diehards like to keep the general aviation slider at 0%, but most reasonable people keep it at or below 40% when airline is around 60%. Airport vehicle denisity is best left at none or medium (at medium it adds the fuel truck). Road vehicles should never be higher than 12%. Boats should be at 19% and 19% respectivly. I know you guys don't like putting your traffic this low, but its the best way to get a descent framerate.
This concludes the display settings, if you all wanted to know my exact settings our (with my rig below):
1680x1050, In game AA, target framerate=unlimited, trilinear, global tex. res. very high, advanced animations, DX10, Lens Flare, Light Bloom, high-res 3d cockpit, aircraft light illumination, aircraft shadows, aircraft self-shadows, level of detail radius large, mesh complexity 100%, mesh res 10m, tex. res 7cm, water effects high x2, land detail textures, ground shadows, scenery complexity dense, autogen very dense, special effects medium, cloud distence 60mi, detailed clouds medium, airline traffic 20%, general aviation 15%, airport vehicle low, road vehicles 0%, boats 20%, no aircraft labels (for realism purposes). (NOTE: I'm using MyTraffic X (DX10 config), that's why the airplane sliders are low)
No matter what skilled PC pilot (or real-life pilot) you are, FSX can be accustomed to your caliber, from almost arcadish to full blown reality. I'm not going to go over the self-explanitory ones, but I will explain a few...
P-factor is the oppisite reaction of the engine spinning the propellor, which makes your aircraft yaw to the left (note this is for most prop aircraft, most multi props, and all jets don't have this issue)... to have this at max doesn't get to reality (because ive flown props), but it gets close.
Gyro modifies the gyro instruments to be more like real-life...and that basicly means worse, because when you do aerial manuvers it can confuse them, and sometimes they will fail. (NOTE: some gyro instruments in the cockpit are the artificial horizon, and turn coordinator)
True or Indicated speed. True speed is actualy what distence your covering over time (most modern day GPSs have a true speed gizmo) and Indicated speed is given from the amount of air going into your pipe on the outside of your aircraft, thus it determines airspeed, which is the most realistic option.
The others seem self-explanatory, but if you have any questions on em' let me know.
Controllers and settings:
Here we will go over various joysticks, why you should have a joystick and the settings in FSX.
Okay the 4 best HOTAS (Hands on throttle and stick) systems out there are:
1. CH fighterstick+Pro throttle ($200-$250)
2. Saitek x52pro ($150-$200)
3. Thrustermaster cougar ($200-$215)
4. Saitek x52 ($90-$125)
if you want the best flight sim experiance in any flight sim, one of these is highly reccomended to use (NOTE: The systems are rated in quality from 1-4...IMO), they have over a hundred functions, excelent reliability, customer service, and control. Google them for reviews and videos on youtube for more info.
However, there are some of us who dont have that kind of money for a joystick, so here are a few that work queit well:
1. Saitek Aviator ($40)
2. Saitek Cyborg X ($50)
3. Logitech Extreme 3d Pro ($35)
Those are only a few, there are more out there.
There are also two sets of rudder pedals for the ltimate experiance:
The CH pro pedels and the Saitek pedels, both are equelly good, and about the same price at $110.
There are also flight sim yokes if you want to fly like a real civillian aircraft, both Saitek and CH make a good product. (about $120 each)
All these joysticks can be setup in FSX, or in a software provided by the manufacturer.
Ah, the reason we can keep playing FSX is because there are hundreds of add-ons out there (they are expensive). There are two-types of add-ons: Freeware and Payware. You can download free addons at places like avsim, simviation, and surclaro. Be carefull though, most of these add-ons are junk. And then, there's payware which includes all the best stuff...here are some neccesisary add-ons to get first:
Ultimate terrain x, MyTraffic X, Ground enviroment x, and Real enviroment extreme. All of these are of the highest quality, with the greatest support and customer service...I HIGHLY reccomend ALL of these, no matter your PC. Because ultimate terrain and ground x actualy make the ground look better and increase fps by a couple. My traffic gives you more traffic for the same performence (plus real-life liveries and military traffic). And REX makes the clouds look almost life-like, along with the water...obviously these will have a little toll on your performence, but they're highly worth it.
Now for aircraft add-ons...there are a few that our the favriotes of the FSX community, and they are: The new Iris F-14, and The Aerosoft F-16
Both of those are the best payware aircraft around, but they're not the only ones...check out these stores:
google for others, but those are my favriotes.
FSX community sites:
If the GS FSX forum bores you, here are some sites to see for sims and FSX.
If theres something...:
you didn't see here, feel free to pm me or ask. Or if I can't answer, check out those sites above.
EDITED ON 1/16/09* alot of the guide was edited, especialy on ATI drivers, make sure you check it all out!