In a slightly 'other view' opinion: As a technical person in a certain field, one shouldn't expect clients to know half of these things, or even to take account of them (even though in most fields, if you change your mind about you want, the result is likely to take longer).

Thus, in your first contact with a new client/customer, these things should be laid out in the original contract, or whatever it is. Even with less formal, 'internal' clients, effort should be made to make sure these things are clear. Write them down, hang them on your door, whereever. Thus, when such a problem comes up, you can point to that document, and say 'yes, sure we can do that, but, it will take longer..'.

Another item:

• Know in advance how you will *test* the results, dont think about it after the project is done. (This usually helps define the actual spec).

C.