For aiming, lets say with a sniper. Okay, if you see your target and there not moving, thats a good shot to shoot. If your target is moving and again, you have a sniper. Lets say there jumping two, wait till they hit the ground and try to get a headshot.
With a Assualt rifle, I'd say just shoot were ever, shoot them a bit then quickly, snuff, them so they die.
Spartan lasers, can be tricky. Because, when your trying to shoot them they, can see the red light. When they run out of the way you get some time, so I'd move it towards them. OR, you could also get a team-mate, to distract the player and then you shoot them.
I would continue but theres alot of more weapons,
my favorite will be know
.
The energy sword,
This is a very useful, tool. Better when your invisible, and have over shields.
So what you want to do, is lunge at them.
How?
well, when your far, but on them you see red, you lunge at them. And kill them right away.
What else?
Needler,
I don't use these.. I hate them. Haha, But when your up close just keep shooting it, they'll explode (the needles) inside of the person and they'll die. thats a easy "noob" strategy, as I've heard.
the shotgun, The best technique, for that is close up, when your infront of someone for example shoot them, in the head. and 1 hit k0, or just close range and there dead.