Originally Posted by EvilMike

1. Don't kill a single enemy.
2. Don't collect a single item. Every item counts.
3. If you can shoot things down to avoid collecting them, do that.
4. If you collect an item by accident, reload.
5. When you DO collect ammo, try to make sure you put it to good use. If you get bouncers, see if you can use them to shoot down other items. Same goes with other types of ammo.