well... i might know a few things, 1. dont attract attention to yourself, (dont fire at the target if u know u wont get it)
2. Stay hidin, being a nod black hand sniper is ok if your good at head shots cause your invisible if u dont fire.
3. go for head shots, (personally, thats were i always go) INSTINT KILL,
4. try not to move around no much unless they figured out were u are, if they dont c u, swich spot constantly, unless u know u can get a shot off before they can,
thats all i can think of now,
-Happy sniping