Pretty much it comes down to mastering mobility which you can get better at by simply playing. I personally have a preference to the alternator SMG myself though I know a friend who doesn't go without his LMG so I think guns are purely what you prefer. As for titan it's good to know their pros and cons and what range they are built for. Read up on their skills set and weaponry. A good example is while Northstar and Ronin are light armor titans they actually play pretty different. Ronin is an in your face hit and run while Northstar is a sniper.