Well.... I can offer some advice.
1. Find a gun you like and get good with it. Figure out its range, how many shots it takes to kill someone, the recoil, how fast it overheats, is it better to burst it or hold the trigger. I use the DLT-19 and after some experimenting with the other guns, I like this one the best.
2. Sensitivity and Reflexes can play a part in being good. Mess with the sensitivity a little. Try it at max, at min, in between, just experiment until you find a setting you like. Reflexes, well, the older you are the harder games are to play, reflexes help, but outplaying your opponent by your map placement or just using your mind to flank, wait to attack, etc... can be your greatest weapon.
3. Play smart, play as if you are really on the battlefield and it is your own life on the line, not just a virtual life. Might be dumb advice, but it works for me. It really depends if you want to have fun or be good or win. Some think it is fun running around trying to get kills and others think it is fun sitting back, playing slow but careful. Some try to win at all costs and some don't care if they win or lose. Some play for K/D. Personally, I hate losing. I rather have no fun and win then have fun and lose. I rather go 5-20 and get objective points and a win then going 20-5 with a lost. So, structure your game around what you want to get out of it.
4. Get a vehicle. Preferably, a AT-ST. Camp the **** out of there spawn points. I trapped the whole team inside a ECHO base exit and just sat there waiting for them to come out. Ended up with 25 kills in five minutes and kept a good chunk of the team occupied from the objective points.
I mean I could go on and on
I like talking about game strategy and stuff
Not sure what game type you play the most. For me it has been an even split.I like Drop Zone a lot more though. Basically for that game, I always run to the pods and activate those. I find a good spot to sit and defend it the best I can on my side that I am watching. Hope this helped a little.