I want to make a cheap mirror, is there any tricks to make aluminum foil reflective so you can at least see a good bit of yourself in it?
You should be able to find some that is already reflective. If not, you need to polish it. Use 3M wet and dry emery paper, starting with about 400 grade, ending with maybe 1200 grade. Then use metal polish. It takes a long time doing it by hand.
Go with the one that is recomended for glass. Be careful as when you reflect light you also reflect heat so if it pointed back out of the house and you have dble pane windows it can blow the seal or even crack the glass.
Aluminum foil already IS reflective, at least on the shiny side. The trick is to avoid crumpling it. You can try carefully gluing a piece of foil, shiny side up, to a piece of cardboard, masonite, or thin plywood (use a gluestick on the cardboard or whatever) then rolling it smooth with a brayer, rolling pin, etc.. Here's another approach to consider - use Mylar, like from an old helium balloon, or you can buy rolls at party stores. If you need just a smaller mirror, get an embroidery or quilting hoop (thrift shops often sell them inexpensively, and you can get them in sizes up to nearly 2 feet in diameter) that's at least 1-2 smaller than your Mylar piece, then stretch the Mylar evenly in the hoop. Presto - instant mirror! If you don't want to mess with the hoop, you can just glue the Mylar to cardboard, Masonite, etc. - Mylar doesn't crumple nearly as badly as foil. If you have any good thrift shops near you, take a look there for mirrors - you may find you can buy a used one as cheaply and more easily than you could make one.