Sand paper and lots of elbow grease then get some polishing rouges and but a buffing wheel for your electric drill and go at them with the rouge and buffing wheel. My advice, don't do it, way to much work, but if you want to there you go. Just start out with a courser grit sandpaper then gradually work to 220 them use the rouges. Go from the coursest to the smoothest and buff it untill it shines like you want them too. Afterwards I recomend clear coating them for ease of cleaning and upkeep.
I wouldn't go with anything courser than 220 at all. Maybe start out with that and work your way up from there until they start shining up. Then use the rouge and buff. They will be much shiner and you will see less imperfections. Good luck, watch those elbows.
If the rims are pitted then you will have to sand. If not then use red scotchbrite and go all over the rims. You will have to get a high speed buffer and polishing compound made for aluminum. It comes in different grits. Check with Eaastwoods. They sell kits to polish rims. Also there are places starting to crop up across the country that will repair rims and polish rims. If you take it on yourself it will take awhile to do. Best to make it a winter project when there isn't much else to do.