My preference is to scope well, give the client a per-project quote and then charge hourly for out-of-scope work. This way, the client knows what to expect to

My preference is to scope well, give the client a per-project quote and then charge hourly for out-of-scope work. This way, the client knows what to expect to pay from the start and if he introduces changes on the way he knows it is going to cost him extra.