The stuff from the home centers won't last (as posted above and many times before by others), especially with a muriatic acid prep. The formula for an indestructible floor that lasts is as follows (I have one):
1. 10-mil poly moisture barrier on the tamped soil.
2. 4' x 8' sheets of 1/2"-thick high-density closed-cell foam with heavy foil on both sides, laid on top of the poly moisture barrier ($10 per sheet).
3. Heavy steel mesh installed on wire stands.
4. Pour 4" slab (6"-8" in leg support areas if you plan a 2-post lift).
5. Let new slab cure for three months.
6. Steel shot-blast the floor to clean the surface and open up the pores in the concrete "skin" so the epoxy has something to grab onto.
7. Apply first coat of 2-part industrial epoxy, allow to cure for 24 hours.
8. Apply finish coat (tint to desired color) of 2-part industrial epoxy, lightly sprinkle fine silica sand (NOT "play sand") on it before it sets up, for anti-slip when wet. Allow to cure for 48 hours, then drive on it.
Mine was done this way five years ago and still looks like it was poured yesterday, and is warm and dry all year round; the poly barrier and foil/foam/foil insulation makes all the difference. The floor is impervious to all automotive fluids and chemicals, tires won't stain it or lift it, Michigan winter ice/salt doesn't affect it, dropped tools don't chip it, and it's super-easy to keep clean with a soft-bristle push broom. It's a "forever" floor if there ever was one, and the light color and high reflectivity doubles the lighting effectiveness in the garage.
These folks did mine:
http://www.homeprofloors.com with their standard "Classic Floor" system - was $1.90/sq. ft. five years ago, turnkey, for the shot-blasting and epoxy coating; best garage money I ever spent.
