My stomach is sloshing around.
That means you have taken in too much carb-heavy stuff and the body has shunted water there to dilute it. This doesn't mean stop drinking, it means that your muscles are getting dehydrated and your critical balance is off?you will need more fluids (with sodium) and perhaps some salt to help move that fluid out. Avoid eating solids for a while, sticking to Coke, broth and gels if you can.
My reflective stuff is gone; am I in trouble?
Nope, they'll give you something when it gets dark.
It's way hotter than anticipated; how can I adjust?
Your body will need more fluids, both internally and externally. Drink at every aid station. My routine is as follows: Run in, grab sponges to wipe face and squeeze over head and body. Pour water on head as I still run. Stop at the sports drink or coke person, walking 20 to 30 steps so I can take it in. Grab ice in cup (or hat) as soon as I leave so I can stay cool until the next station. Repeat sponge routine if able.
More: Dehydration: The Worst Case Scenario
My calf / foot / quad / hamstring / whatever is cramping; what can I do?
Slow down as it won't go away. Walk it out and try some light stretching. Get in some salt as that might help, but know that adjusting your effort / gait will be more immediately effective. If possible, go into your Triathlon Time Machine (patent pending) to fix that part of your bike when you raced to the top of every hill at 54 rpms.
More: How to Prevent Race-Ending Leg Cramps
My fingers are tingling; how can I fix it?
Get some potassium in your system, aka a banana.
Transition
I can't find my transition bag.
Hopefully it's out of order, and no one else took it. Look around and grab a volunteer (or three!) to help you out. You can't go anywhere without it, so hopefully it'll turn up soon enough.
Do I put my bike shoes on and run in them or carry them?
I almost always say put them on, because once you have your bike you'll have to put it somewhere in order to put your shoes on, and that's not easily done when everyone is racing.
Should I change into a complete bike outfit after the swim?
Ideally not. Even if you want to wear proper bike shorts, you can still swim in all that stuff under your wetsuit or speed suit. Putting lycra on a wet body is wicked hard. Save yourself minutes and energy by wearing as much as you can.
Should I change into a new outfit for the run?
Some folks love the fresh feeling of new bottoms, others don't. It's up to you. Just know that you will need new socks and a hat for sure for the run, at the very least.
Random Questions
My timing chip fell off.
If possible, you should stop at the next transition or penalty tent, or flag down an official on the course who can radio ahead to have it ready at the next transition. It's not super critical as they'll have pictures of you out there. You can also tell folks at the turns, "it's me, #1423 with no chip!" so they can take note.
This is really hard; will it get easier?
Not during the race it won't! You signed up for this and you are ready; race day is 90 percent mental so do what it takes to get mentally right so you can tackle your day. Before you know it, that finish line will be less than a mile away and you'll be floating along until you cross the line!
More: 4 Keys to Ironman Execution
If you are looking for our Four Keys guidance, you can find that in the official Four Keys of Triathlon Race Execution post.
Search for your next Ironman.