if you don't have an air popper you can also put the kernels in a brown paper bag that you have folded over [do not secure the bag with any metal!!!] and pop them that way. if you have quick hands and a decent pot you can put the kernels in a lidded pot and pop them on the stove with no oil or butter, you just have to watch and move the pot so that the kernels don't burn. somewhat tricky, but doable. and they also make glass and plastic air poppers for the microwave, though i have never tried either of those.
-google first. ask questions later.