polishing them up isnt too tricky, just very time consuming / boring!
assuming yours are still lacquered, youll have to strip all that off, then sand out any pitting , diamond cut lines etc. start with the highest grade paper you can get away with, aas you need to work your way up through the grades of wet and dry, ending up with an even, satin silver p1500 or p2000 finish.
be warned, that can take many hours of arm aching boredom! i've yet to find a good mechanical way of doing it without risking taking too much metal off.
after that i use a drill mounted polishing kit i bought from machine mart. a coarse wheel and compound all over starts the shine, a buffing wheel and finer compound improves it, then a final hand polish.
maintaining them is another ball ache, to keep them gleaming they'll need polishing at least weekly, to keep a proper deep mirror shine like c76jons on his m3 they need cleaning after every journey
i dont have the time or energy for all that, so a nice shine is enough for me.
and don't even think about using them on a daily through the winter. salt will start to pit them within hours