A lot of times I'll find a slight bend in the very end of the shaft. Depending on the quality of that end, I will either use the opposite end for the nock (if its better), or I'll go ahead and cut to length and then us it for the nock. Usually, I don't have to cut to length prior to selecting the nock end.
Yes, the grain MUST be horizontal while nocked. Any compromise in the grain can result in injury if the grain fails. Having the grain horizontal will minimize this risk.
Tomorrow I'll go over staining, dipping prep and dipping.