Just some handy tips:
- Play on easy. Always.
- Use a machine gun or, if all else fails, an automatic weapon.
- Play with someone who is better than you.
- Hide out in a corner facing the doorway.
- Pick a character that is balanced all around.
- Or a character that has a shit ton of health.
- Lean with your controller. That and pressing the buttons harder will always help.
- Use AI players as shields.