Mass Effect 3 - Starting character

[Grognaurd]

Strategy Spoiler

I run side to side and watch the Beam, after it tracks a bit, it fouls and goes up above you, I run under the beam and light up the reaper. I also did not always paint the target to completion. Pull the trigger to start the targeting and if you see the red beam again, start running. After the reaper beam is out of the way, Light it up again. Since you have already started the targeting, the second painting will be much shorter

[Hellbringer]

Strategy Spoiler

I run side to side and watch the Beam, after it tracks a bit, it fouls and goes up above you, I run under the beam and light up the reaper. I also did not always paint the target to completion. Pull the trigger to start the targeting and if you see the red beam again, start running. After the reaper beam is out of the way, Light it up again. Since you have already started the targeting, the second painting will be much shorter

That was the hardest part for me while playing on Insanity level because the beam loved tracking me in addition to the fact that after the 2nd or 3rd shot, the reaper would start shooting as soon as I started up my targeting laser.
Pissed me off big time, but I stayed the course and finished on Insanity.