To salt the rims of margarita glasses, take a slice of lime and run it around the edges of the empty glasses to moisten them. Dip the moistened rims into a container or wide bowl of margarita salt, and gently rotate the glasses to coat the entire rims.
There are several brands of margarita salt, which is also called "rimming salt." Some labels include Master of Mixes, Jose Cuervo, Bar Maid and Spazazz. Margarita salt is a coarsely ground salt that is available tinted or untinted. Other coarse salts, such as kosher, fleur de sel or sea salt, can also be used to rim margarita glasses.