1. Check the wall surface. Use a level to make sure the wall surface is level horizontally and vertically. Fill in low spots with drywall or surfacing compound, let dry, and sand the wall smooth.

2. Locate baselines. Use a tape measure to locate the wall’s center, and use a level to draw horizontal and vertical guidelines. Start at the midpoint and plot out your tile pattern by aligning a single row of tiles in each direction. Adjust the spacing to minimize cutting and waste, if possible. Use a level (or framing square) to mark the final baselines.

3. Apply and test mastic. Spread mastic on the wall for one or two rows of tile at a time, using the smooth edge of the mastic trowel. Then create V-shape furrows with the notched edge of the tool. Before you add a group of tiles, press a single tile into the mastic and remove it to make sure the mastic is evenly distributed on the wall. Voids or thick deposits of mastic can weaken the bond. Repeat this test each time you apply a fresh swath of mastic.