I agree with Track Rat, I don't normalize or use noise reduction. Also agree that you need to make sure the track is "clean." Otherwise, as he says, copy/cut/paste, overdub or re-record as required.
After that I usually don't do anything further to the track - except to set a rough volume level - until I have all my tracks recorded. EQ, for example, at this point without all the tracks present is a waste of time IMHO. (Although at times I might add compression at this stage if I have a very uneven track.)
The only real difference I have from TR's approach is that I save my volume envelopes until I have all the tracks. I do a lot of vocal harmonies, and to get the right balance among the voices requires them all to be present.