It all depends on what the vocal requires. If it was recorded well enough sometimes a lot of processing isnt necessary. Also it could be the order of your vocal chain thats throwing off the mix. Some say eq before compressing, others say the opposite. It really depends on the recording itself. If you've done those things and the vocal still isnt sitting right you might have to add a delay to it, reverb, parallel compress, additional takes . . . etc. The possibilities are endless. It really boils down to what your aiming for.
Is it a track that doesnt require a lot of stacking on the vocals? Going for that pure sound? Try adding reverb and/or delay to give the vocal depth. Again you could parallel compress it to give it that extra something that it might be missing.
Is a track that does have a lot of takes/adlibs? Maybe use less effects on the lead and only process the adlibs/fill ins.
Ultimately, again, it all depends on what your shooting for and there isnt a step by step formula. It all depends on what your trying to accomplish and remember there is no wrong way as long as it sounds good.