Well for me it certainly helps that I usually have clear requirements up-front. Designers for instance take a lot of the guesswork out of what I need to do for

Well for me it certainly helps that I usually have clear requirements up-front. Designers for instance take a lot of the guesswork out of what I need to do for website work. For other things, like debugging legacy code, I just tell clients that I need time to diagnose the issue before I can give an estimate.