Here's some. If you got others, post them:
Hydrate the dry before, start the race well hydrated, hydrate throughout the race. Don't overdo it to an extreme tho.
Electrolytes tablets in your water bottles.
Protect yourself from the sun. Wear a cap or visor to shield your head, face, and eyes from the sun’s burning rays.
Don't forget your sunscreen.
Don't forget your sunglasses.
You could put ice cubes in your hat.
You might adjust your pace to the heat.
Go heavy on the body glide to prevent chafing on the bike/run.
Use the spray stations along the course, if provided, and at the finish to cool off.
Some extra salt on pre-race food perhaps.
Eat your electrolyte-intensive food: goos, banana, etc.
If wetsuits are banned: you may not float as easily, you might be somewhat slower, but you'll have freer range of arm motion.
Here's some more:
For quick and refreshing recovery, make sure to stop by the DC Triclub tent and cool off in one of our 2 state-of-the-art kiddie pools, filled with ice, compliments of Ryan Troll. Even more incentive to race fast and finish early: the pool temps (much like the air temps) and the sweat-to-ice ratio will both go up precipitously as the day wears on!
There are also rumors circulating about a possible slip-n-slide... but news sources (mainly this message board) have yet to confirm these sneaking suspicions. Personally, I'd like to see the slip-n-slide run the last 10 meters of the course, stretching across the finish line (thus helping people build up speed for the Blazeman roll! That would make for some great race pics (particularly if there is a photo finish!)
Wow... it's chilling to read this post for the first time 4 years after I almost died from severe heat stroke at the General Smallwood Triathlon. Less than a day after I made this post, I collapsed about a mile away from the finish line with a blood temperature of 106.7 degrees. I made a full recovery (PTL!), but not before being air-lifted to Prince George's County Hospital where I spent 5 days recovering (including 4 days in the ICU). That ended my season, my triathlon career (although I do shorter races now and I've PR'ed at everything 5K and under since then), and any thought I ever had of racing in those conditions again.
Ed has some great suggestions for everyday race preparation... always hydrate well, wear sunscreen, sunglasses, etc. However, in extreme conditions which arise a few weekends a year, the best suggestion may be to skip the race, long run, or hard workout. I wish I considered doing that 4 years ago. If you are racing this weekend and you are concerned about the conditions, please seriously consider skipping the race... your times are not going to be ideal and the race won't be as much fun as the next one under more ideal circumstances.
I'm happy to talk about my personal experience with heat stroke with anyone who is having concerns. PM me and I'm happy to chat any time.
Just my amateur opinion, but I would also add: Train in the heat (or the conditions your race will likely be)
You won't be ready for a hot race unless you've trained in same/similar conditions. Most folks like to run/bike in the morning before it gets hot, but when you're racing, you can't control the time of day you start running/biking. Ditto on the swim. Swimming in a temperature controlled pool is different from swimming in open water in the heat and humidity. When I train for hot races, I make it a point to do some of my workouts in the hottest part of the day in full sun.