I use the guestimating software package. Its free, well almost anyway. I put a dollar sign associated with all the key icons using them as a unit and then count. During this process I get interupted and then start over several times. This cycle repeats till I can get all the way around the building or room. Then I write it down and multiply it out. I make a note of problems or errors on the prints that will need to be addressed (spelled change order$). I then go to the next item on the key. I write it up thinking of all the stuff to put at my atvantage and fax it over to them. You can hear them having the cow over the phone later. I double check using total costs vs electrical costs as a percentage, or sometimes square foot costs verses what my square foot costs are.