Practice, stick with it, and this game is greatly rewarding.
One of the most frustrating parts of this game is the difficulty and learning curve, which are both incredibly high. The game doesn't have any introduction into the career, so you just jump right in and have to get it right, and there are still stunts I haven't 100 percented yet, and I got the game when it was releases! The upside to this is that the game is really rewarding. The prizes for completion of stunts are good, but to have a game where when you finally beat a level, you gasp, stare at the TV for about 20 seconds, then to actually jump up and dance is a great self-esteem reward, although you might not want to play Stuntman in front of your friends, as you will probably ignore them for a half hour playing one level, and then dance and make a fool of yourself.
Stuntman was, and still is, a great game in about every way. Atari, heed this call! Either make the Driver series like 500% better, and/or make a sequel to Stuntman, Please!!