If you get the boss class snipers, use them against light vehicles as well, but they're inneficient at normal sniping since they will be easily detected and are twice as expensive making death both more frequent and more costly.

Try and use the environment to your advantage. hide behind a simple rock or buidling whenever you can, and peek out to snipe. avoid moving too much. Always take out enemy snipers first, preferably with headshots, then anyone who might be dangerous to you, and then engineers. Us engies hate that But I stay covered...

A few quick shots might be better than a long headshot. They won't know where it's coming from right away and may mistake it for something else, and you might not have time to line up.

Always, Always, Always go to your sniping positions as covertly as possible. Hide behind the harvester or large vehicles on the way up. I usually get killed out in the open minding my own business while some infantry or sniper does eeny-meeny-miny-moe and picks me. Make sure to scope it out and be quiet and stealthy until you can strike.