Underlayment

• Granite tile is so hard and solid that it's easy to believe it's indestructable. It isn't. It will crack on a floor if there's improper underlayment, just like any other hard tile. The best defense against that is 5/8-inch cement board, which looks like drywall sheets but provides the strength of cement. Lay cement board sheets over your wood subfloor, cutting them by scoring with a razor knife and snapping, securing them with carpenter's glue and drywall screws sunk every foot or so. Tape the seams as you would drywall, but use thinset mortar instead of plaster. Sand the surface smooth after it dries, and you'll have a good, solid bed for the granite.
  
  

Cutting

• Granite can't be scored and snapped the way ceramic tile can, because it's too likely to break badly due to the natural veins within it. It's so hard that even a standard wetsaw could have problems cutting it, so make sure you use one with a good diamond-edged blade, and go slowly. For countertop edges, the sharp edge of the tiles needs to be beveled off, which you can do by setting the tile on a homemade jig that holds the back end up at 45 degrees while the edge of the front is run along the saw blade.
  
  

Installation

• Granite should be laid out like most other floor tiles--from the middle, using intersecting snaplines as your guides. Granite tiles should be laid closer to each other than most kinds of tiles, though, with grout lines of just 1/16th of an inch (use plastic spacers) because the idea is to give the impression of a solid slab. Use cement-based mortar as your adhesive. As you press the tiles into place, hold a small level across every two pieces you lay to ensure they're even with one another, pressing one or the other deeper into the mortar as necessary. Grout with non-sanded grout (because of the thinness of the lines) and make sure the grout fills the lines completely and is even with the tiles on both sides.