There are some things your AC may need to be aware of at any time during a mission or Arena battle.

1- If you have an Exceed Orbit (EO) core, launching the pods can increase your heat, so if your AC is not good with heat, use this wisely.
2- Never equip a vertical missle and a missle canceller. Once you launch the missle, it'll just blow up.
3- OB-INTENSIFY may increase all abilities, but damage will increase.
4- On certain arena battles, Trene City is not the answer. If someone relies on a vertical missle, or anything that requires height, use the parking lot arena to your advantage. (Ex- Carom)
5- Your opponent can actually shoot your weapon out of your hand, so look out.
6- In the Arena, if small missles annoy you, go to Trene City, and rather than scaling the huge building, climb on top of one of the walkways leading to one of the smaller buildings and stay there. You will still at times get hit, but not nearly enough to kill you.