Find a good spot that gives an overview of where the enemy team might congregate...'crash site' makes this easy...you know the enemy team will rush to the site...you can support your team from a distance.
Try not to go nutz firing off shots when you see a target...keep a beed on a target untill you feel confident the shot will hit...make sure you get your second shot off quick to finish the target off. Or work on targeting their head. Keep practicing and don't get flustered.
Also when you do find a good sniping spot...don't hang around it too long...always have your next spot in mind while in your current location. Maybe after 2-3 kills...move onto another sniping location....cloak while traveling...cloak while reloading.
For sniping class mods I use:
PROXIMITY ALERT- (lets you know if someone is close to your position or even has sniffed you out)
VISION ENHANCED- (it will highlight enemies in a red aura...you can see the red aura when they hide behind walls or bushes)
RETRIEVER-(saves you from having to go out in the open to grab your tags...and level 3 reduces the amount of tags needed for killstreak rewards)
I use DSG-1 with:
SILENCER and EXTENDED CLIP
SNIPER SCOPE (for double zoom option)