I've put three coats of poly urethane on my headstock (to cover a newly applied logo) and I'm brand new at this sort of thing.

Can someone explain "wet sanding" to me in detail?

Is three coats enough or should I add more? Should I sand between every subsequent coat?
What grade of sandpaper should I use to smooth the finish?

Any more advice would be great.

Thanks as always for everyone's help around here!!

Wet sanding involves using a lubricant and 'Wet/Dry' sandpaper to smooth out a finish... typically between coats. I use 600 grit with warm, soapy water, sanding in little circles, almost a buffing motion. Dry with a towel and let it air dry between coats... Start with 600 grit and gradually increase in fine-ness (?) through 800 and 1000... I also like the very fine ScotchBrite pads...

It's been awhile, but I usually sand every other coat to let the finish build up... After it is sufficiently thick, I'll go to every coat... I'm sure that others will be along shortly to properly instruct you :)

-robert

Robert - thanks for the advice, man!