If you have Battlefield 3, go Recon and use rifles without the scopes. Ironsights are fun and good practice for close combat against SMGs!
If you're position is obviously unknown by the enemy, take your time. If a guy moves past, report his position. Never waste a round if you know he's gonna come back out giving you another chance.
Rifle nades are kinda like Panzerfausts. They both fire in an arc, and both have a decent blast radius. As well, both are used against infantry :/. Useful for combatting groups too far to use normal grenades, which are useful for getting the guy hiding behind that door over there.
If scoped, you don't have an excuse not to go ranged shooting. Then its a deer shoot. If you miss his nice ears will hear a whiz and flee. If you take your time, and if moving, aim ahead accordingly, it'll take a round and you'll get your venison/points.