Use the grout saw to dig out the grout from around the first tile you want to remove. Press the carbide blade firmly into the grout with both hands and press it forward and back, breaking it up. Get as much as you can out without damaging the wall or the surrounding tiles.
Hold the end of the chisel into the space where your took out the grout, along one side of the tile. Position the chisel at an angle with the tip pressed on the line where the tile meets the wall.
Hammer gently at the chisel, hitting it into the base of the tile. Move the chisel over by a few inches and repeat, tapping it against the base of the tile all around. Continue until the tile pops out.
Repeat for each tile that you want to remove. Use your metal putty knife to scrape the wall clean of residual mortar or adhesive.