Considering the lack of save during combat and your early inital weakness bad accuracy, the high accuracy of the aliens and that being shot is a very bad thing
i found the best tactic early on with my snipers and long range weapons is to shoot and not get shot back
I do this by hiding behind a building, rock or other solid defence step out, kneel fire a snap shot preferbly at an alien not looking at me
( aimed shot take too much tv)
stand up and duck back into cover
while i could stay out and fired mutiple snap shot or 1 aimed shot if i miss i'm open to being shot
although the success of this tactic will depend on the Reaction fire of the alien and having something to hide behind
you can call this tactic cowardly but the aliens outnumber me 10,000 to 1 and the battlefields are littered with bones of 'brave' men