Good fences make good neighbors just as good contracts make for good developer/client relations. At the very least your agreement with your developer should contain a complete description - in non-vague terms - of each feature to be built as well as a paragraph description of the overall project.

He emphasizes that, if the feature or change is not included in the documentation from the start, it's not a part of the project. Making assumptions on vague definitions will only cause problems down the road, so be specific in what you want.

If negotiating the contract with your developer is a hassle, consider it your last opportunity to walk away and find another developer.