Sniping is very easy in this game, but still a bit of a challenge for me because there really aren't any true sniper maps where I can just hole up in a building and pick people off all game.
Carrier, Standoff, Yemen, Raid, and Turbine are all very easy to snipe on.
Carrier - get to the side with the blast shields and post up on the right side or watch the middle.
Standoff - post up in either one of the large houses at either end of the street. If you angle it just right, you're able to watch a good chunk of the house, the street, and the broken wall without exposing yourself to a ton of gunfire.
Yemen - if you start on top, the right building is awesome. You can watch the plank path, or go to the upstairs and watch the left side building, as well as the street below you. You can also go left and watch the tower and the staircase, or stay back in the fruit stand. If you start on the bottom, you can snipe from the big window on the right side. It's also possible to take the right side building and still have the other team spawn at the top.
Raid - take your pick... I wouldn't watch the round area, but you can do that. I think you're exposed to too much gunfire if you snipe there, though. If you start kitchen side, watch the middle. Or, you can get in the pool next to the wet bar and snipe into the bedroom and below it. If you start garage side, you can either sit in the bedroom or sit in the middle. Again, I wouldn't advise going into the art room overlooking the round area.
Turbine - Building 2 is good. Building 3 is good. Building 4 allows you to overlook their spawn if they spawn near the bridge. The pathway between the ruins and Building 3 allows you to watch a huge portion of the map. The bridge is a good place to snipe from, although I don't use it often. Sniping from the top of the turbine is a death wish if you stay there for longer than a few seconds.
I hate the vast majority of snipers on this game because they ALL spray with the SVU or run around and hip fire or quick scope you. I really wish the sniping was like that of World at War, where every sniper rifle except for one was bolt action.
I hate how Treyarch has catered to people who use cheap tactics so much. Sniping used to take a degree of skill to do effectively; now all you need is an SVU with a Ballistics CPU to keep the sway down and a Variable Zoom Scope, and you can spray n' pray to your heart's content.