Since I'm an ex-member of (SAS) or "Stealth Action Sniping" I've picked up a trick or two since I started playing.
Never pull the trigger unless your sure you'll hit. Pulling that trigger and missing means you've compromised you position and risk being shot. After said shot is fired (if it wasn't a headshot) unload on your target. Stealth is no longer a factor, just be sure to eliminate your target. Watch for enemies trying to counterattack.
Reload in irregular patterns. Many player will wait and count the shots so that will throw them off. If someone is too close, try to "no scope" it. When "no scoping" aim for the upper body first, then unload while pulling up quickly. If you start out trying to "no scope" their head, you might miss and be screwed. When guarding a hallway or stairwell like in Soviet Patrol Base, "no scoping" is very useful. Have an allie stand infront of crouch infront of you, while you stand behind him, aiming you SVD down the stairs. When opposition arrives you and your partner rain bullets on them. This way the enemy cannot kill both, and he's protecting the lower half of your body.
Well that's it for now. Watch for more tips later.