Well seeing how im almost a captain grade 2 i should know alot lol =p
Im not sure is anyone has sad these but here are mine.
1. If you getting chased bounce gernades off the wall and it will problaly kill them.
2. If your versing a ghost or a mongoose or somthing. Let them get close to you then through a spike gernade or plasma then jump real fast.
3. Never stay still while sniping no matter how much u suck at Moving Sniping.
4. If your playing capture the flag always makesure you have a plasma pistol so you can disable veichles like warhogs then stick the driver.
5. Shoot about half a round with the assult rifle then melee them.
6. Use the mauler melee combo shoot them then melee them.