Don't worry about laser sights, I avoided these throughout all shootem up games, they do nothing to help you sight a shot, and as soon as you sight a target it draws a line directly to where you are hiding, start off with a sniper rifle, and/or a good assault rifle, avoid AK47's, rubbish on rapid fire.
A light weight, shorter weapon with rapid fire (not pistols) with 2 or 3 shots per target, will take down faster, than long bursts of fire. That way you won't always be running out of ammo.
Just remember hide first, and shoot first, be a hero if there is nothing else left to do.
When shooting first take out the dudes with with the sniper rifles, shoot anyone else and they will find you.