There are a lot of ups and downs to buildiing your own home. You can safe a lot of money, but the question is how much of a headache do you want? You can be active on different levels. I will warn you, we haven't done this as I have been around the construction business long enough to know I odn't want to mess with it, but a friend who did said that if your marriage is not 100% strong you will not survive building your own home.
First thing is to decide how active you want to be. Do you want to be hands on doing sheetrock and painting and anything else you can and only contract someone to do foundation and electrical and such, or do you want to hire a general contractor to come in and build per your design.
Depending on what you decide you will either contact a general or start studying up on county/city/state building codes.
Which ever way you go, MAKE SURE YOU GET LIEN WAIVERS. And make sure they are real. We have ran into two cases were when we went to file a lien on a property the owner showed lien waivers saying so and so paid us. When in fact we never were. Get the lien waiver straight from the supplier, not your builder. Otherwise you may pay twice for something.