Setting countertop tiles with mortar is an age-tested method that works for most DIY-ers. You may spend a lot of time picking out and arranging a pattern of tiles ahead of time, especially if you're doing a mosaic countertop out of one-inch tiles. There's an amazing range of tiles, including glazed tiles with their options of matte or high gloss finishes. Many homeowners prefer natural tile materials from cut granite, limestone or slate.
The prep-work involves the dry-fit method, laying out your tiles on the existing surface to create your countertop. You can use alternating patterns and colors for effect. A great way to keep things straight is to lay out your tiles on the destination surface, then transfer it one tile at a time to another surface in the kitchen or on a pallet. You can buy tile spacers to ensure straight lines and room for grout at any home improvement store. Another way is to mark lines and patterns on the underlayment by pencil.
Don't mix up your adhesive until you're ready to work, and only mix up enough adhesive you can use up before it hardens (20-30 minutes). Countertop adhesive is typically used in thicker consistency than adhesive used for laying tile and stone floors. Think of peanut butter.
Putting down the tiles
Set your edge tiles first. Thinset is the adhesive of choice among many contractors. Use a notched trowel to lay down the adhesive, carefully avoiding covering the layout lines. Trowel the adhesive into an even plateau.
Be sure to set only the whole tile pieces first, saving cut and fill pieces until the end. Push the tile into the thinset and rub it in to ensure full adhesive coverage. Use a level as you go to ensure a flat surface. Finally, set your cut perimeter tiles. Always face the cut end toward the backspash, sink, or the sides. If your fill-in section is small, you may want to individually "paint" adhesive directly on the back of the tile and set it in its place.
Get out the grout
The last step in laying down tile countertops lies in the grouting. Pick your grout carefully. A white grout on a kitchen countertop is sure to darken or pale. If puzzled, buy a few small bags or boxes of grout and try it out with leftover tiles.
Remember: too much or too little water will cause grout to either run or crumble. Use only a fresh, consistent mixture based on the manufacturer's instructions. After the grout dries, use a piece of cloth to polish it up.