1) if the vehicle is in good condition, don't get out of it in the enemy base unless you want to know what it looks like to be killed by your OLD vehicle. I have stolen a few enemy vehicles that were abandonned in my base because they went to repair it, or tried going into the building. Just use the vehicle on the building for as long as you can.
2) If you are an Engineer and going into the fight on foot to keep the hardware in 1 piece, pay attention to when they back up. Usually that means there is something there, move with the vehicle.
3) If you are Hotwire or a Tech. and you are placing mines, remember there is a limit to how many mines can be placed at 1 given time. I think it is 30, please correct me if I am wrong. I made the mistake when I first started playing by placing mines all over the place, and I go back to where I started and the mines are gone. So don't just place mines anywhere, make sure they will be effective. There is nothing better than you repairing a building, and you hear "BOINK".

And 1 final consideration. I have done this in the past, I just purchased a 1000 credit character, and the base get over run. You hear a the builing you are in is under attack, and taking damage fast. I will take the loss of money and change to an Engineer or Hotwire/Tech if i have the $$ and repair the building.

These are just things I do, everyone is different, but remember you are on a TEAM, and as the saying goes, "THERE IS NO I IN TEAM