We'll be there in no time...AND THAT’S JUST THE POINT.
When somebody says “they’ll be there in no time”, you desperately need to remind them that is exactly the problem - you have “no time”.
The first thing to do when prepping for a shoot is to get all crewed up at least an hour before you thought you’d need everyone there. If it isn’t a problem with lighting, it’s a problem because Talent arrive 10 minutes late for makeup - or the guy next door to the location just bought a jack hammer and wants to play with it all day - (“Can I buy you a case of beer to stop for a few hours”? - “nah mate, I don’t drink” - seriously??).
Check wardrobe the day before, time-out your scripts - try reading them out aloud, not in your head (in head reads are usually faster) and don’t forget a hard drive to transfer all your digital media at the end of the day.