What difficulty do you normally start with?

Depends on the game really, varies a lot for me. Usually set shooters to hard as I find them easy games in general. RTS games generally normal because I suck (despite it being a favourite genre)... I might set a JRPG that I've heard is particularly grindy to easy even as I'm not into that! I like it when games let you manage difficulty either on the fly or with each level etc. It's nice to have the option.

I would say more often that not I just leave it at the default though and go from there.

Most games hard if they of an incentive of some kind plus it helps the game last longer.

I usually start and play most games in hard. It lengthens the game and makes events seem and feel much more important. Harder difficulties than that can seemingly cheapen an experience for me however, because in most case that puts the game at an unreasonable amount of difficulty for the sheer reason of being difficult and not much else.