Shop_rat,
I'm a journeyman tile setter. Putting in a granite tile countertop that looks good can be tricky, the key to a professional looking job is the sub surface prep and layout. A mortar bed is the best sub surface, but I would'nt recommend the average homeowner trying to float motar without some previous experience.
I would put down 3/4" exterior grade plywood as a base. Thinset and screw down 1/4"or 1/2" cement backer board over the plywood. Make sure the sub surface is rigid and FLAT. (I think Hardibacker sucks, and I never use it. It is made of compressed paper sheets and cement.) Next, get some straight pine stock and screw it to the edge of the plywood where the wood trim will go (make sure it is level and true). This will act as a guide as to where the tile will terminate and also serve as a guide to set the tiles level.
Lay out and dry fit all the tiles BEFORE you start stickin' 'em. I use 1/16" shims. Even if you butt the tiles together there will be a grout joint, as most all 12" granite tiles are beveled along the edges. Use a 'marble and granite' type thinset to stick the tiles.
Use a dark, unsanded grout. Lighter color grouts will stain in time. Epoxy grout would be best to use, but it's not as easy to use as cement based grout. The thing about epoxy grout is that once it sets up, that's it. It's harder than Supermans knee caps, and damn near impossible to remove without scratching/chipping the tile.
Remove the wood guide boards and install the wood trim. Get a color matched caulk to use between the trim and the tile, grout in that joint will crack over time as the wood expands and contracts.
Easy, right?
There is a book I recommend to homeowners. It's called
Setting Tile, by Michael Byrne. Published by The Taunton Press. It's a good reference with solid techniques. You can do the job yourself and have it look good, just take your time.