People forgets and re interprets; including clients, especially common customer clients without prior experience in engaging your kind of service, the basic foundation of how your business runs, and think they can adds up additional features without us having to spend extra efforts or time.
Worse is, if you have some sort of written contract where everything is still widely interpretable. That would some day resulted in few loose cannon, rampant, maverick assumptions, than when claimed by the people you do the work for, would sound highly related to the words written on the said document — though on your defense it does not.
Well there’s little that you can do by then when it’s out; and quarrellings over something happened in the past with just vague documentation is time and effort consuming.
Chain the beast
The best mean to prevent dispute from happening down the line is to prepare up front the specific and detailed scope and specification of what you will deliver in exchange of the cost you incur; in the software development world such document exist in form of SRS (Software Requirement Specification).
SRS outline the development direction as well as specifying deliverable details. Be as definite as possible during development of this SRS, leave the minimum to interpretation and assumption; even better write down what your assumption are, to leave out the potential of making “assume” fulfill its hidden meaning of “making ass out of u and me“.
Though it may seem like a lot of work, and sometimes you have faith in your customer’s intelligence and familiarity with the nature of creative works, or are counting on their good faith and good intention, disputes might still occurs. And anyway you can only get to know about your client after repeated involvement with them, and crooked clients do exist.
Do have a good expectation about your clients, but also have a good defence measures to protect yourself from possible misshapen down the path. (byms)
*Clint Eastwood image is from http://www.almightydad.com/parenting/smoking-bad-cowboys-cool