Measure the first shower wall from side to side, and find and mark the middle.
Draw a line vertically up the wall, from the floor to the top of the cement, using your level and pencil.
Spread thinset over the bottom half of the wall with the notched trowel, covering it all from the floor up about three feet.
Set the first tiles in the mortar along the bottom, on one side of the vertical line. Put spacers between the tile and the floor to create a gap there.
Hang the rest of the bottom course of tiles side by side, putting spacers between them and below them. Cut the last tiles on either end to fit at the side walls, using a wet saw.
Hang the next course of tiles above the first, again starting at the center line and building to the sides. Repeat, working your way up the wall row by row. Use the wet saw to cut the end tiles as needed and to cut around the shower fixtures as necessary. Tile the entire wall and the other walls.
Allow the mortar to set for 12 hours. Pull out the tile spacers.
Spread your grout over the newly hung tiles with a grout float, starting at the top and working your way down. Press the grout into the spaces between each of the tiles, while scraping it off the surface with the long edge of the float. Let the grout sit in the lines for 10 minutes. Wipe up the excess grout with a dampened flat sponge.
Let the grout dry 24 hours. Run caulk lines along all edge of the tiled walls, where they meet the floor and each other. Let the caulk set 24 hours before using the shower.