played quite a bit of MP and all spartan ops (level 20 right now), i am farrrr from a halo expert, but this is what i have learned
1. head hit box is huge, i have been getting a lot of headshots and i know i am not that good...so just aim near the head when killing someone
2. i didn't play with the assault rifle at all, but after getting smoked by rtweezy i tried it, next game 32-6! (i was lucky to break .500 on most games) if it is close up combat that thing just smokes people, i will just stay in hallways, etc.. so i don't get in a long range battle and people will just run towards me and i will smoke them..
3. i like the ammo "perk" there have been numerous times the other guy runs out of ammo, but i still have some bullets left
4. seems to me (could be wrong) the BR is a little quicker to kill close range and the DMR is better at long range, i was "sniping" people with the DMR, but when people got closer the BR would win...
5. liking the active camo, numerous times it allows me to get the first shot off, thus allowing for the kill
6. on big team be sure you have plasma nades, i have gotten numerous multikills by sticking vehicles
7. been said before, but stick with people, it is close to impossible to kill someone when you have 2-3 people shooting at you...
8. on big team if you get some people to work together and get a bunch of vehicles and hang out near the other teams spawn, they don't have a chance, because they will never get a vehicle to combat you, beat a team 1000-450, doing that..
hope that helps... anyone feel free to correct me, like i said i am not an expert. I am really liking this game, having a lot more fun now that it is not a situation where people just remember where the best weapons are on the map and i don't stand a chance, game feels very balanced, just about everytime (outside of the lag going on) i get killed it is because i deserved it.. this is the most fun i have had playing halo this gen.... much better than 3 and reach IMO..