Never give someone a quote

There are some customers who insist on just getting a piece of paper with a price on it. Those customers are setting themselves up for failure. The development process cannot be reduced to simple numbers. A client may not understand this, especially if they are unfamiliar with the process.

I have repeatedly seen the naivete of customers who do not understand that scope creep invalidates a written quote. Similarly, that if the customer fails to communicate requirements, they cannot expect the developers to deliver what they need. I like to put it in the same terms as building a house, because that usually rings true for most people. When you do not express your desires to the architect, nor examine his work-in-progress, then you should not be surprised if what gets built isn't what you wanted. Likewise, when you ask a contractor to make a change, you expect a bill above the original work order. Software development is no different.

Do not blame the customer. Do not think badly of them. It is your responsibility as a project leader or solo developer to manage your customer's expectations. Teach them what they do not know. A piece of paper cannot do this. It takes a personal touch.