The wall should be strong and flat, surface be smooth. The wall should be waxed / printed. Wall should be clean and dry, if the tiling has to be done on plywood the surface of wall should be sealed with 50% volume mixture of PVA and water.
Apply a high quality ceramic adhesive on the wall and place the first tiles on the corner. Apply even pressure on the four corners of tiles to ensure adhesion of tiles to substrate. Cover the Area of wall that can be done without cutting tiles and leave it for at least 12 hours. Cover the rest of area with measured and cut tiles as per requirement.