Let's collect some game play tips

Thanks for the tips.

After a lot of practice I sometimes have good games now - I'm not reliably on the top 5 but I get there now and again.

In getting gooder - check your leaderboard (select) it pops up fast.  Play as the Assult trooper, stick with your Squad Mates or higher ranking players and follow them about.  Cover them, kill 'share' (you'll get assist more then likely) , watch how they handle the various situations of defending, attacking, where to go for objectives.

 - this is just an 'at first' suggestion of course.  Don't annoy people once you get your footting.  then it's better to work as a team, but with some distance so you can flank in open area and cover two directions at doors and choke points.

Bounty Hunter Card will net you more points on everything you do, along with the other suggestions of chasing the objective this can open up the enforcer, ships, whatever A LOT faster.  I personally find it very useful to getting ahead and adding some power to your game.

For the heavy the key to my improvement was learning to rapidly drop the shield and sentry to regain my speed and mobility.  They're both useful for pretty specific situations and need to be dropped the moment that situation ends.

Officer - Well - about getting gooder... I take the officer and follow a heavy - I'll drop the turret at any important point and then I back up and I'll shoot over and around them with the officer.  You can keep your meat shield healed and rank kills or objective points while getting some strong cover. 

 - Officer - as above - I pulled a blue recharge command from a crate and use it to keep allied Heavy's shield and sentinel abilities fresh.  I tend to favor the officer and running teamwork this way - whether the other guys know it or not.