I've been doing this for 10 years and each time, for each new project when I have to give a quote, I sit looking blankly at my screen and come up with a estimated number of required hours 10 minutes later.
For my regular client (those I know won't change their minds 10 times), I often give a fixed amount as an all-included package. As I normally underestimate the time it's going to take, I multiply my estimate by 1.5... Sometime I loose, sometime I win.
Do you have a form or a particular method to estimate your time on a project?
I'd like to have a better method than the total guess I'm doing now (I have enough experience so it's an educated guess, but nonetheless...)