[zachrose]

I work with two types of documents: master consulting agreements and work orders. The master consulting agreement has all the "standard" stuff like IP, confidentiallity, indemnity, etc. The work orders are where I specify what we're going to do(1), how much it's going to cost, and when it will be delivered. Both are dated and signed. This works well for me and allows me to do agile-style sprints with work orders. This is usually in addition to a ballpark price range for ballpark scope.

(1) Where "what I'm going to do" can be substituted for "what I'm going to try," when the client understands why I can't guarantee something.

[Argorak]

That, I do a lot as well. Basic point being: a fitting contract doesn't have to be a hassle.