To fix a loose shower tile, you need first to remove the tile so you can replace the adhesive. First, cut out the grout using a utility knife. Then, loosen and remove the tile using a hammer and a chisel. Next, use a chisel or a screwdriver to chip away old grout from tiles. Then apply a layer of your new glue to the wall with a trowel. Remember to apply a layer to the back of your tile as well. Press it into place and allow it to set. Then, mix your new grout and place it into the lines around your tile.