Simply play through the campaign. Training missions and co-op missions do not count.
General gameplay tips:
- Memorize the level.
- Find and exploit all possible paths.
- Take your time when you can.
- If an AI bot is bearing down on you, never stop moving.
- Play the tutorial first.
- Watch your time.
- All the gold does is add more time to the clock. Know when you can go for it and when you shouldn't.
- Read the name of the level. It may give you a hint as to how to play it.
- You can switch zoom levels by clicking the right stick. One will give you a complete look at the level, one is standard playing level, and the third is a close-up. All of them come in handy for different parts of the game.