When considering a color for your stained driveway, look over the concrete really good and note any existing stains.  The amount and color of the existing stains should be considered when picking your color.

Black Tire marks almost always come up with a good cleaning.  The things that won't come up are: 

Rust marks - the metalic ions in the metal(s) have reacted with the concrete to create color (most often a burnt orange color).  This color  is there to stay and can't be removed without causing potential damage to the acid stain color.

Nuts - as in Pecan and acorns.  Once these are crushed under a tire, the natural oils in the nut combine with the meat and the shell color; they are most often there to stay.

Battery acid - this is a strong acid that will eat up all the reation material in the concrete.  However, this can be blended by the use of dye stains.

Paint - paint is always bad for concrete.  It gets into the pours of the concrete and may result in a spotty appearance in the finished product.

These are the most common things you will find that affect your project.  Some can be overcome by choosing a stain color close to the existing stains.  Some can be blended with dye stains. 

Any existing defects in the concrete may stick out to you because you know it is there.  But, in the hands of a good stainer, these blemishes will be hard for a friend or visitor to find.