Preparation is key to successful racing. So do and I say, and not as I do, to give yourself the best possible advantage.
Do take it easy on the days before your race. Keep your weight off your feet.  

Don’t carry a bag the weight of another human on your back for the best part of a day while wearing flipflops. Your feet won’t thank you for it.

Do get a good night’s sleep the night before and the night before the night before your race.  

Don’t try and do this on a 13 hour sleeper train from Chiangmai to Bangkok. Those curtains, surprisingly, don’t cut out much noise from your fellow passengers and the shaking of the train isn’t helpful.

Do drink lots of water. Especially if you’ve chosen a race in Thailand where it’s 35 degrees. Don’t stop drinking. 

Do hope for the best when on asking at the race expo if there are toilets on the course the official smiles and walks away.

Do get to the race expo early to ensure they haven’t run out of t-shirts in the size you want.

Don’t have a tantrum when the official explains that the number on the front of your bib is your age grouping and that yours bares a big fat 30.

Do take the time to make some new friends at the race expo. The guy on the left here is from India and will be running the half marathon barefoot in about 2:15. Respect. The guy on the right is from China and didn’t know there was a half marathon happening until I asked him if he knew where the expo was. He came with me and decided to sign up. Respect to that guy too.