The proper printer and the proper decals.
I use an HP LaserJetP1102w. The toner cartridge is 85A. Pretty much any printer that uses an 85A cartridge should work for the decals. If you look at the MSDS sheet of a particular type of toner you can find out the percentage of iron ferrite in it. Below is what you are looking for. Ferrite is an ingredient of toner, powdered iron, at high temperatures in the presence of air, it will become iron oxide. For example, the Lexmark 260 MSDS listed the percentage of ferrite in the toner as 7-13%, where the HP is 45%, giving it more durability. I have only used the 45% one. (Thanks to Ed Lay for that info!)