I think Yo has defined the 3 levels quite nice, what i would add is to make sure you set expectations. Each level would come at a different cost point, due to the time involved and the amount of detail worked out. I usually have up front conversations with the client and find out what will work best for them while at the same time i will provide them a sample (sometimes i even include a image in the quote along with the concept phases to show the end out put.)
Chevis W