For the new players, here's my quick advice,
don't think of this like a gears of war, where you are bouncing around, trying to get shotgun kills and dodge roll better than your opponents. Similarly, don't just hang out in one position, you'll get killed that way. Instead, keep moving from cover to cover, and engage when you have an advantage. Think of this as a cross between Panzer Dragoon and Full spectrum warrior. You're main goal is to find a way to get around your opponents cover, and hit them while they are exposed. The most effective way to do this is through tactical movement, watch where your opponents are engaged, find an open route, and haul ass through till you can get a clear shot.
If there's not an open lane, that's where the other elements come in, now you need to force your way through, the best way to do this is abilities. Grenades are awesome for this, toss one out, and it will force your enemy from cover, or get you a kill to open a lane. Other options, use siphon and dance around in the air, pinging enough shots to regen health. Use the armor boost and fly at a dudes face with a shotgun. send a couple of drones for distraction and make a kill shot. There are lots of ways to handle it.
Sometimes though, you'll just find yourself in a situation where you and another dude are in the air, this is basically a MP version of an on rails shooter, move like crazy, and keep fire on the other guy. If you have more skill, you'll win.
When the match starts, take a look at your team, see what they are choosing. If no one has the radar pick that, it will make your whole team better. If no one on your team has a bunker busting kit, grab one (Grenades, syphon + MG, Armor + shotgun are some common ones). As the match starts, check your teams layout, if they are concentrating on one path, check the other, you'll either stop their team from advancing, or find an open lane to get some nice flanking kills.
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