I'll spend a few minutes before a shoot to walk around with a meter and take some test shots to know what the outcome will be before I have to shoot for "real". I look at it this way with 500 shots taken and 50 to present; I can spend 20 minutes before understanding the areas in a venue, and/or a few seconds to check my settings before the shot I want.
If at all possible I also go to the venue a day or two before the event and "stake out the joint". It allows me to see what lenses/other equipment I will likely need, and to store some custom White balance readings in to the memories. Also when time is not pressing I find I can give some unflusstered thought to potential creative locations. Basically do as much as you possibly can before the event to take the pressure off your shoulders on the day.