Set the sheets of mosaic tile in the room where you are installing them. The tile should be the same temperature as the room before beginning installation.
Examine each sheet of mosaic tile. Set aside any sheets with missing or cracked tiles. Remove the cracked tiles by peeling them off the backing sheet. Set aside one sheet to use for replacement tiles.
Check the wall surface for nails or bumps. The wall should be clean and flat. Lay a drop cloth at the base of the wall. Remove any outlet or switch covers.
Use a pencil, a measuring tape, a plumb bob and a 4-foot level to mark a 3-foot grid pattern on the wall. Use a chalk box to snap the lines on the wall.
Mix the thin-set cement in a bucket or trough. Mix the cement according to the manufacturer's directions.
Start at a bottom corner and apply thin-set cement to that section of the grid. Use the flat side of the trowel to apply the cement, and then use the notched edge of the trowel to remove the extra thin-set and provide a "tooth" for the mosaic tile.
Press the mesh side of the sheet of tile against the thin-set cement. Knock the tile, gently, with the grout float to ensure all the tile makes solid contact with the cement. Use a tape measure to measure from the edge of the tile sheet to the nearest chalk line, and adjust the tile sheet if necessary to bring it square by sliding it slightly with your hands. Use a straightedge ruler to make sure your grout lines within the sheet remain straight.
Press the next sheet into place, using spacers if necessary to keep the grout lines between the sheets the same width as the grout lines within the sheets. Follow the same procedure as above for mounting the tile sheet, squaring it and keeping the grout lines straight.
Continue installing the mosaic tile sheets on the wall, working in one 3-foot grid area at a time. Cut the sheets, if needed, to fit in the last spaces against the corner and ceiling. Cut the sheets by separating the tile along the grout line using a utility knife.
Replace any missing tiles within the sheets. Apply a small amount of adhesive to the back of a loose tile and insert it in the empty space. Use tile nippers to cut any tile that needs to be cut during the installation.
Wait for the thin-set cement to dry according to the manufacturer's directions. It usually takes about 24 hours for the cement to dry. Remove the protective sheet, if present, from the surface of the tile sheets after the cement has dried.
Mix up the style of grout recommended by the mosaic tile manufacturer, either sanded or non-sanded grout. Use the grout float to apply the grout to the tile. Press the grout into the grout lines, working both horizontally and vertically. Work in a 3-foot-square section at a time. After you have filled the grout lines, wipe the grout float across the tile at an angle to remove excess grout.
Wait until the grout begins to dry. Check the grout manufacturer's directions for the recommended amount of time; it is usually less than an hour. Wipe a damp sponge across the surface of the tile to remove grout from the tile surface. Use light strokes to avoid removing grout from the grout lines. Rinse the sponge often to keep the tile clean.
Use an old T-shirt to remove any remaining grout haze after the grout has dried. Buff the mosaic tile with the T-shirt to remove the haze and shine the tile.