Looked up your account at Halo Waypoint. You must be doing something awfully right as your kill/death ratio shows as 1.58. I'm pretty sure that's a good thing.
My BPR is only 51, but I do suppose I'm real Halo veteran, so here's some pointers.
-. Shoot to kill. If there's cover nearby your enemy is going to duck to, and you don't have a frag ready, there's a big change he'll surprise you.
-. Jumping is, in fact, the key. It makes Halo unique, and also, you that much harder to hit. Especially handy in short-mid range, or to disorient your opponent.
-. Master the DMR. I hate the bloody thing, and I hated the battle-rifle before it, but yeah. Master it. Learn to pace your shots, and practice locally on moving dummies. You'll get the hang of it.
-. Power-weapons are Win-weapons. Look up where all the big guns are on the web, or offline practicing. Rocket-launchers tend to hurt.
-. Abilitiiies. New, and handy. Even sprint is great when you're in need of quick cover. Just think carefully when using it; they're often more of a last resort life-saver than anything else, and armor-locking with the enemies closing in on you.. is not very pleasant. Jetpacking should only be used when you have a place with cover to go to.
-. Shoot, and when your shields go down; take cover. Live to shoot another 4 seconds later usually helps.
-. Vehicles may be big weapons, but they're also big targets. Think twice before entering one. They explode this bit faster than you think they will. I'd also like to point out Ghosts are not invulnerable to Assault Rifles and the Pistol. You can blow it up if you throw enough at it, if you can avoid it's tackling and fire.
-. Sniping works, but more often works when they can't fire back. Always have a wall and/or a teammate near.
I'll gladly play with you! Gamertag is Dae Ravenheart. You can also find my page at Waypoint on it.