This is a great subject and already I see lots of great answers. Personally, I quote at night- it is SO time consuming. I also call it a Repair Estimate these days which gives me the ability to ask for more if I hit problems. I use my iPhone if I have additional repairs I run into and snap/ send a picture to the decision maker as the job is taking place.
My repair estimates read: Parts and labor to....
That way, in the unlikely event I am able to beat my own optimistic quote the extra is mine :). Customer doesn't know how much is parts, how much is labor. Years ago on my road trip reports I would provide time on, arrival time, leave time and time off. Huge mistake and unnecessary. My experience is the customer is much more concerned about a QUALITY job at a perceived fair price. If you hit a snag, get your decision maker in the loop as soon as possible. His biggest concern is keeping his boss happy and that means he can explain what happened because he knows what happened.