Here is absolutely the one and only tip / tactic, I have deduced so far in this game, most of the time just do as I'm told to do, or follow someone else. Don't know some of the maps that well yet...
So this tip is for a gun, particularly how to be better with a certain gun, one that i've heard people claim not to be any good.
L1A1:
Aiming this bad boy is hard due to it's iron sights being so obnoxiously in the way.
My tip is, in order to see potential victims aim lower towards the ground than your horizon or where you're looking if it's far enough range to even be using this single fire weapon. Once you have an enemy zeroed in your eye sight, raise the iron sights to match the enemy, pull the trigger and with any luck he should be dead.
*only tip i have to offer to date*
Well here's another one, always check your corners and your 6.
But that's just common sense.
No Sights = Luck, period.