Here's a small one from me regarding mouse sensitivity/twitch reactions, take it or leave it but I've been in some top clans over the years so like to think I'm not too 'n00b'
- Aim straight ahead, fix your cross-hair on a rock or whatever
- Close your eyes
- Using your mouse, look behind you (as close to 180 degrees as possible)
- Open eyes
- Adjust mouse sensitivity lower/higher
- Repeat until you are actually opening your eyes and staring at what you were expecting