Remove the grout from the perimeter of the tile you want to take off, using your grout saw. Dig out the grout by pushing the carbide edge of the blade into the grout and scraping and breaking it down. Get as much of the grout out from around the tile as possible.
Hold the tip of your chisel into one of the spaces created by the grout removal. Angle the chisel back.
Tap the chisel lightly with the hammer three or four times, until you see the tile start to come away from the wall.
Move the chisel over to another part of the same edge of the tile and repeat. Continue moving the chisel and tapping it with the hammer until the tile comes completely off the drywall surface.
Repeat the process for any other tiles that you want to remove.
Scrape away any remaining adhesive or grout from the drywall with your razor scraper.