It may seem like a no brainer (which is usually good for me on a race morning) but checking your bike gears before the start is a great idea. I fully intended to do this on Sunday but then there was the whole covering Ruby with a mile wide tarp to consider. OK Sunday morning while I was airing up the tires (also another great idea) would have been optimal. But I didn't. And "lucky" for me, I hurriedly took Ruby in on Saturday to have a little tune up and gear adjustment.
Starting out on the bike was hampered by my race belt mishap (stupid bib tore while I was trying to turn it around) so by the time I started pedaling I was already flustered. I went about a mile and thought, "Why do I suck?" (Even more than normal). I looked down and realized, oh, I am in my big chainring. The big chain is great for really speedy flats but it takes more out of your legs. So I was pumping along wondering why my legs felt as if they were pedaling a tricycle. Now I know. At least I didn't fall over when I started pedaling.
So the lesson is: Always Check Your Bike Gears Before A Race.