First off, if there is any type of paint or clearcoat on the item, strip it with some aircraft stripper available from your local hardware store. Get the surface ass clean and rare material as possible.

Second. Sanding. This will be the hardest and most painstaking part. Start off with a rough grit to get all the rough casting down and smoothed out. For EVERY grit you use, sand untill the scratches put in by the paper is all the same. Move up some grits when you do. I reccomend and electric sander for grits all the way up to 600. When you get to 600 grit, start by hand and sand again till all the scratches are the same. When you get to 800 grit, wetsand using either water or WD40 as your lubricant. Sand till scratches are all the same. For the best shine the aluminium has to be smooth. The smoother it is the more it shines. Go up to 2000 grit and stop.

Next, clean the rim throughly to get off water and wd40 you might have used.

Last but not least, buffing. To get the best shine I reccomend getting a buffing kit like Wenol offers. It comes with wheels and compounds. Start off with a medium buffing wheel and Black Rouge (compound) Hit it up with that multiple times. You should be blingin' already. After that is done, take some White Rouge with a lil softer buffing wheel and hit it up a few times.

If you are doing a rim or anything that contacts with water and what have you clearcoat them. Professional if you can.