For the best reflections (chrome-like) I fully recommend Mothers Billet polish. A couple applications makes a big difference over just one. Don't rub hard, rub longer. :bigups
If you're looking for a less expensive alternative, but *almost* as good a look, I'd go with Mothers Mag and Aluminum polish. Close results, but not quite as Mirror-like as Billet.
IMHO, of course.