Practice.
No, I'm serious, that's all you can do.
Practice.
Edit: You'll find that you get much better at the game as you go on. For example, there is one mission in story mode (6 or 7, I believe) in which you have to escape a building under a time limit of 50 seconds. After trying for half an hour, you'll barely squeak through with less than a second to spare, and think that the designer were sadistic to give you so little time.
On the next difficulty setting, the time's been reduced to 45 seconds, and after an hour you'll find that's enough.
Then you try the third time, at 40 seconds, and you start to feel that the previous two really WERE over-generous, because you've gotten so much better in such a short time period.
In conclusion: Practice!