When you're sniping and you can see the person's name it's always best to pause while you shoot. For whatever reason when you stop it hits the person a lot more easily. If you don't stop the shot can go in random directions. A time when you don't need to stop is when the person is really close to you and you know you have an easy shot on them. If you need to snipe from a long range and you can't see the player's name that you're trying to shoot, get out you're swingshot, then hold R2 square and walk forward.
Once you let go you should have a magma cannon out. If you're using a different weapon and you switch to the sniping rifle you can see the persons name for about two seconds. Switch to the Magma Cannon and back to the sniping rifle to see the person's name while shooting at long range. Also, you always need to look at the person you are trying to shoot. Also, it takes practice to snipe so if you can't hit anyone just wall snipe. To wall snipe hide behind a wall, come out of the wall, shoot the person, and go back behind it so that they cannot shoot you. This is the best way to snipe without scoping.