What you wish you knew on your first photo job

If you could go back and talk to yourself as you were walking in to your first portrait session, wedding, commercial shoot, or whatever your first assignment was; what would you tell yourself?

I've got two.

1 - Make sure you check ISO when you walk through doorways.  I have a whole series of shots that were done outside at 1600iso.  I was so caught up in checking everything else that I forgot to change the setting back after being in a really dark room without a working flash, which is actually related to #2.

2 - Check and make sure you're flash is attached snugly.  My first paying shoot was for a friend's wedding reception.  I had bought a new flash (Vivitar 285) and a bracket.  We had been there about 5 minutes and I pulled the camera up to my face and the flash went flying.  It still flashed, but only at full power and only every 4th shot.  Fortunately both my wife and I were shooting so I stole her flash, but now we each have 2. 

I'm sure I could think of more, but I'm curious to hear what suggestions y'all would have.

This is hard.  My first paying wedding was actually a blast.  Amazingly nothing went wrong and I had the second biggest album sale of my career (although with my prices raising over the years it wasn't the wedding I made the most at, by far).
But here goes - I wish I had known something as simple as changing my flash batteries to fresh ones throughout the reception.  I was waiting forever for the flash to recycle and didn't realize what the problem was.  (I know, I am dumb)
I also wouldn't have taken as many overall dancing shots, I was just so enamored with the high balcony and all the partying that I took like fifty pictures that all looked the same of the tops of everyone's dancing heads...
I still have shots from my first wedding on my website   I sometimes wonder if the better I get the less amazingly lucky shots I get...

There is something from each job that I wish I had done differently or wish I had known, but that's life.