What are some tips for installing a small shed?
Any place that sells pre-built sheds in your area would likely have advice on site preparation for delivery.

I don't know what the soil's like in your area, but if you're going to hit bedrock before 42", it'd likely be easier to put in a slab;  If you're likely to hit lots of tree-roots, the slab might be a better choice (so you don't kill a tree, and have it fall on your new shed)  For most other times, I'd personally go with footings, but I live in an area that's clay and easy to dig.  (other than tree roots).

Some pre-built sheds are made to sit on a slab, as they have no floor; this can make it easier to get things in/out of the shed, as you don't have the step-up.

... also, rather than buying from Home Depot or similar, look to see if there are Amish or Menonite areas near you -- they often have businesses that do this sort of pre-built structure construction.  It might be a little more expensive, but you can get them customized to a specific size, material, etc ... it's what I'd do if I wasn't going to build it myself.