Well Ya, from my experience to hit a moving target you just have to lead - aim in front of them. The distance you aim in front is determined by how far they are away.
Tip #1: Always snipe from a prone position if possible - it's more accurate
Tip #2: Relocate as much as possible - it saves the enemy from finding you.
Tip #3: Try not to shoot at moving targets - be patient and wait for the perfect shots.
Tip #4: If you're spotted, run like hell, unless it's another sniper or AT you don't have much chance.
Tip #5: Be patient. Wait for targets, scan the field, know the map and enemy movements. Spot targets for artillery as well and tell your team about what the enemy is doing.
In answer to your questions - Snipers generally have low scores because they mostly shoot at good oppurtinities, for example, a guy sitting in a MG, and don't kill many foes.
For better hints and tips go here ->
http://www.planetbattlefield.com/bf1...er/index.shtml