Personally, I think the most important lesson for any sniper or rifleman is to be able to find protected firing positions.
Example: just the other day I was playing on Danzig on the RTR server (thanks to whoever undid my ban) as a soviet rifleman. At the start, I always like to go to the top of the 3 story building and do a little sniping. I got up there with our sniper who promptly proceeded to kneel in front of a window and get shot in the head by the german sniper.
You never look out of a window in this spot on Danzig. Instead, you look diagonally to the east and west. There are penalties for this: it's difficult to rest your weapon and you can't cover the main street coming to the bridges. In exchange, you get to live.
My kill/death rate for that part of the map has to be in the hundreds, or even thousands to 1, not because I'm a particularly effective rifleman, but because I don't die very often.
Similarily, on Konigsplatz, I'll rarely peek over the top of a hill. Instead, I'll lie along the reverse slope of a small mound and snipe as the enemy walks across my line of sight. I'm vulnerable to people coming directly at me, but that's what teammates are for. It also encourages you to shift position frequently.
Back on the mod, when sniping on Berlin I used to stand in the rear of a building and snipe out windows in an entirely different ROOM. Windows are evil. Windows let bullets through in two directions, after all.
Just my $0.02