The best method I have used is to heat them with an iron. Wet a old washcloth and place the iron on it over the seam you want to start with. Wait a few seconds then move the iron. You will have to experiment with the time it takes for the adhesive to get soft. Use a putty knive to remove the tiles. This is a sticky job. After the tiles are up use a solvent to remove the rest of the adhesive from the floor. This worked great on my oak floors with 2 layers of tiles.