Re: cjdave- welding ?
Good advice so far -
If it's sticking in the tip the feed's not fast enough.
Something that helps too is the welding spatter jelly. Plunge the entire head in it - wipe off the excess, it helps the spatter stop from sticking to the tip and wire -- especially very useful in out of position welding where spatter falls back into the head, like upside down. One can of the jelly lasts forever. The spray's good for stopping spatter on the work, but the jelly's great on the head (welder's, not yours.)
Sticking to the workpiece is another story altogether - indicates feed's too fast, you are traveling too slow, or you need more gap.
A roller than lets the wire slip occasionally can drive you nuts.
Get proper roller tension by holding the head a few inches - 6 - 8" above the cement floor pointing right at the floor - pull the trigger. Let the wire push against the floor, then bend. The wire should bend and still feed evenly. If it hesitates the rollers need more pressure.