When you're about to engage near your enemies base, It's better to kill them one by one in front of you and always run for a cover. It's always best to charge the enemy base with a squad and stay undetected as possible. Never ever take the time to humiliate your opponent(tea bagging, waiting for them to look at you and kill him,etc). Be careful and stay alarmed at any time, You don't know when someone might pop up and scare the living shit out of you
And for god's sake, Don't just charge and go Rambo with the SMG, Doing so won't do you anything unless you're a no life pro gamer or something. Always take your time and be a team player. It will always lead your team to victory and if Enari's in your team, Go ask him to make an Intel tower. He makes good ones and gives you 30% chance of winning. Think of it as a lucky charm ;)