DIY bathroom tile installation is no longer the challenge it was before the Internet came along. Although the process for installing tile is virtually the same, and bathroom fixtures around which you'll need to install your tile are the same, you at least can usually find somewhere on the Internet information for completing most DIY projects such as installing bathroom tile.
Preparing for Installation
You'll find that your installation goes much more smoothly and without as many mistakes if you make needed preparations before actually gluing your tiles. Clean and dry the surface on which you plan to glue your tiles. Remove the existing tile and pre-fit your tile before gluing it down. Lay all tile pieces as they will be finally laid when you glue them. It will also mean that you'll need to cut tile pieces to fit around fixtures and to fit at the edges of your floor where whole pieces are not likely to fit. If you fail to do this pre-fitting, you will likely find that your tile pattern is not consistent. Finally, you'll need to find the exact center of the room, if you expect your pattern to be consistent when you're finished.
Applying Tile Adhesive
Applying adhesive is not as simple as just starting to apply it at any edge of the room. First, be sure you are using a notched trowel to apply the adhesive. It will better ensure that the adhesive is spread evenly. Without using this trowel you'll likely have areas of the floor where the tiles will fail to adhere because there's not enough adhesive. Begin where you've marked the center of the floor. To space your tiles evenly as you lay them on the adhesive, use spacers.
Preparing to Grout
Your adhesive will need 15 hours to set. Once the adhesive is set, you can begin removing your spacers and mixing your grout. Each brand of grout may require specific drying and application directions, so you should check the instructions on your adhesive.
Grout application goes more smoothly if you apply the grout with a rubber float at a 45º angle. Wipe the excess grout as you go. If you wait to remove it when you're finished applying all the grout, you'll likely find that some of the excess grout has dried and will be harder to remove. A damp sponge works best for removing excess grout when it's still soft.
Approximately 1 hour after you've finished applying grout, you should check to see if there is any grout haze on your tile. Clean any you find. Finally, because the bathroom is often moist, warm, and humid you should use a mildew-resistant caulk to seal the edges of your tile.