How to Install a Tile Backsplash

Turn off power to the kitchen, and remove outlet covers and switch plates in the area to be tiled. Tape off outlets, cabinets and the area where your countertops meet the walls. Move freestanding appliances away from the walls.

Using a level, attach a ledger board (a sturdy piece of lumber attached for support). In this case, we are using a straight 1x4 board screwed to the wall studs where you want the bottom edge of the backsplash will be. A ledger board temporarily supports tiles until the adhesive cures, keeping them level where there is no countertop.

Clean walls with a mixture of trisodium phosphate (TSP) and water according to the manufacturer's instructions. Sand or de-gloss glossy surfaces.

Check the flatness and condition of the wall. Fill dents, dips and ripples more than 1/16-inches with joint compound. Let it dry, sand smooth and prime.

Find the centre of the wall that best suits your tile selection and mark a vertical line. Some tile patterns work best when centered on a focal point, such as the faucet or stove.

Dry-lay tiles horizontally on the countertop along the wall using spacers to check the ends. If cut tiles will be too narrow, adjust the layout to allow you to cut wider pieces at both sides.

Check the vertical layout. Cut tiles are best hidden under cabinets, but you may have to cut from the bottom if your countertop isn't level.
First, use a level to find the lowest point of the countertop. Hold a tile at this spot, accounting for a 1/8-inch expansion gap. Mark the wall at the top of the tile. Then, use a level to extend the line along the work area. This line serves as your cutting guide to fit tile along the counter.
To see where the tile will end at the top of the installation, make a jury stick. Mark a straight board using the tiles and spacers for the vertical layout. Hold it up to the wall to check. If you have tiny slivers of tile at the top, adjust the layout down and redraw your reference line.

Mix your chosen tile adhesive, according to directions and spread on a small section of the wall with a drywall trowel. It's important to work in small sections because tile adhesives dry quickly. Comb over it with a notched trowel.
Option 2: Peel-and-stick tile adhesive mats are also available that bond instantly to wall surfaces when pressed firmly with a grout float and allow you to tile and grout the same day, replacing traditional thinset and simplifying tile installation. Use the mats on clean, flat indoor surfaces such as backsplashes, countertops, and tub or shower walls. Avoid using them for floors, ceilings, fireplaces, steam rooms, shower floors, and surfaces that will be submerged in water. Mats don’t replace waterproofing products for tile. Follow the manufacturer’s instructions for installation details. 
Tip: Use white adhesive for glass tile since it may show through.
Note: Don't cover your layout reference lines with adhesive.

Press the first piece of tile into the wall with a little twist, leaving a 1/8-inch expansion gap at the countertop. Press against it with a rubber float to seat it in the adhesive.

Working in small sections, repeat the procedure with additional pieces using spacers to ensure even spacing. If you need to make a cut, mark the tile. For larger tile cuts, set the tile in a tile cutter mesh side up, and score the face. Break each piece along the line. For smaller tile cuts, use nippers.

Let the adhesive dry for 24 hours, then mix grout according to directions.
Tip: Use un-sanded grout for gaps measuring less than 1/8 inch. Use sanded grout for gaps measuring more than 1/8 inch. 

Apply grout diagonally across tiles using a rubber float to press it into the joints. Wait 10 minutes, then wipe away excess grout with a sponge using a diagonal motion. Rinse your sponge often. A slight haze may form but will clean away later with a haze remover you can buy separately.
Note: Do not wipe the grout from the joints when cleaning away excess. Always use a diagonal motion to protect the grout lines and only apply light pressure.
Tip: White-colored grout typically looks best with glass tile installations.

Allow grout to dry according to the manufacturer's instructions, then apply grout sealer according to the manufacturer's instructions.

Fill the expansion gaps with caulk or silicone sealant.

Add box extenders to outlets and switches to bring them level with the new tile backsplash. Replace outlet covers.