Ok here are my *real* tips
where you aim depends on what ping you have
0 = dead on aim, no lead
33 = aim close
66 = aim a little wider out
100 = a little wider than 66
and on and on
aim for the shoulder and shoot left to right as they strafe. But it's all about pratice. I suggest starting in hangemhigh team slayer and practice there.
Good luck.