Glass tiles can add color, glow, drama and 'pizazz', but, glass tiles are less forgiving than other kinds of tiles--it calls for precision and strict attention to details.

• 1) Glass is more brittle; it can scratch so, on counters and floors it is best used as accents and borders on areas nearest walls--areas that do not receive a lot of activity or traffic.
• 2) The tiles must be completely cleaned before you start--I recommend running them through a dishwasher and/or cleaning the back sides with a lint free cloth and rubbing alcohol before you start. Dust particles will show and can create unattractive bubbles and air pockets
• 3) You must use WHITE thin set, not mastic! Mastic does not have the bond strength of thin set and it can discolor and/or yellow which will affect the color in clear or sand blasted tiles.
• 4) The thin set on the wall must be flattened smooth: no grooves or lines, completely smooth; then you must thinly 'butter' the entire back side of the tile before adhering it to the wall. Work slowly, patiently, deliberately and neatly.
• 5) Use unsanded grout and keep in mind that it will take longer to set up because the glass will not absorb moisture. Wipe off excess grout immediately-- you can clean crevices on the surface of my tiles with tooth picks and wet cotton swabs.
• 6) After the grout has cured, clean the tiles and apply a sealer to the grout to prevent moisture penetration and staining.
• 7) Tiles backed with opaque white glass are more 'forgiving' and thus easier to install.
• 8) Never use abrasive cleaners.

For further information and installation tips, I recommend the following book:

Working with Tile (Taunton's Build Like a Pro)
The Taunton Press
Tom & Lane Meeham
Chapter 11: Glass Tile