Another suggestion here. I have built with Habitat for Humanity for years and we usually do our own foundations. In Austin TX, we did pier and beam and an occasional concrete slab. This is a fabulous way to understand how a foundation is built. Construction is a highly visual craft and seeing it for one hour is worth about 10 hours of reading. Call your local habitat and work with them on the weekends that they are pouring forms for a pier and beam or pouring a slab. They are much better at educating you then a contractor because that is what they do (teach you to build homes). A contractor generally knows what he knows but usually is strained to teach a novice what he does and more importantly, why he does it.
As for types of foundations, the contractors in your area will generally be only familia with one type of foundation and will only build that type. (concrete slab in the southern climates and pier and beam in the northern climates all though this can vary)
The main thing you want to find out with any contractor is WHO is going to supervise and what does he/she look for in the work. Concrete work is not rocket science, but there are some important things they need to watch.
Slump of the mix leveling piers and forms before pouring Re-Bar cages (How well tied etc.)