Everyone is wondering how they can level up fast and this is probably the most unknown way to gain experience and points very quickly. Everyone knows how to do challenges, contracts, etc. The game type is a huge factor when it comes to experience gained and the game to be in is headquarters.
Headquarters involves 6 players on each team going head to head to capture one point. It is kind of like domination with only one point. Whichever team catches the flag point will try their best to defend it until the other team "destroys" the headquarters. Every member of your team will gain 50 experience points every five to ten seconds or so, not to mention the solid 200 experience you get for. The longer you hold it, the more points you get.
Many people think that playing ground war is a way to get huge amounts of experience. Yes, you can get a lot but not all of the time. In headquarters if you play for the objective, you'll get at least 10,000 experience points per game. Kills are also still worth 50 experience so keep going for those too, but try getting kills to help defend your headquarters!
This is where my strategy comes in. Most people just go for kills in this game; it is rare that you find a team that always goes for the flag. Get a full lobby of friends who are dedicated to going for the objective and you will absolutely dominate. Everyone on your team will get 50 points over and over again. You get such a huge match bonus it isn't even fair. If you use a full lobby then you roughly get 15,000 - 20,000 experience per game!