Almost not possible to do it wrong. I should say, I haven't had any difficulties.

I haven't taken mine out of the water, but a good question. Usually just cut with a razor blade right at a fork. I've then either stuck the frag down in the sand or in an empty shell or somewhere, they'll attach (and heal) in no time.

Then you've got the catch 22, cause the mother will probably grow even faster/better.

I recently saw an interesting piece on Garf's site about fragging them. I seem to remember them discussing removing from the tank. Also a pointer in using zip-ties to attach in lieu of say rubberbands that could squeeze too much.