Halo 4’s multiplayer modes are tied together by the UNSC Infinity, which serves as a gateway to the game’s so-called Infinity Multiplayer experience. Players are able to customize a Spartan-IV character, and progress through a multiplayer career across both War Games (co-op) and Spartan Ops (competitive) modes, as well as Forge and Theater.
No different than any other game featuring a leveling and progression system, characters will begin with next to nothing, but choices will open up as you level up and earn new unlocks at a steady pace. Earning experience points and levels will allow you to build your character the way you want it, and however you want it to look.
As you make progress through your Spartan’s career, you will be able to unlock and gain access to a wide range of guns, and you’ll also have to make a few difficult choices along the way in terms of Specializations. As you’re only able to tackle one Specialization at a time, you’ll have to live with your decisions until you complete it.
How quickly you earn experience and levels through your career depends on your skill, and staying in-game until it ends is the only way to keep the XP you earn during a match. With the exception of earning XP through commendations and challenges, quitting a game will forfeit any combat XP progress you’ve made during that round.
Halo 4 doesn’t exactly provide you with any built-in charts or guidelines on how to proceed, and winging it as you earn levels through your career isn’t the best way to get the most out of multiplayer. This wouldn’t have been an issue back in the old days when game manuals were around.
With that in mind, a redditor going by lol-jk has put together a progression chart to serve as a guide to leveling up in multiplayer. Have a look: