I have used both BMF and Testors papers successfully. I can get Testors at 40-50% off at Hobby Lobby, so I usually use that.
There are four types of decal paper. Be sure to use the right ones for your printer. There are inkjet papers and there are laser printer papers. They are not interchangeable. Both types also come in clear and white.
I disagree with several of Tom's statements. I have used Dupli-Color clear without problems, but I usually use Krylon Krystal Clear to seal the decals first. Mist coats are important for success. Unlike ink jet decals, laser decals do not need to be sealed before applying. Second, ink jet decals are sadly far from opaque. They are very translucent and therefore do not show up well on dark colors. You can try layering decals, but it is hit and miss.