Train early and register late.

They use your run and swim timings to put you into batches and you want to be in the batch that starts the earliest. Less sun and traffic. You do not want to race in Chennai heat or traffic. Register as soon as your timings are reasonably low. The first batch gets more photo coverage too.

Change at home

The prep email I got said they had changing tent(s), so I decided to change at the venue but when I got there I saw only one extremely small tent for the women. Which brings me to my next point.

Invest in tri wear

It's worth it. At the very least buy a tri short, it saved me a lot of time at T1, I just had to slip on a shirt over my swim suit and start cycling. But it cost me in the run, at 12PM it's like running in the Sahara, air is dry, no shade and I'm cooking in my swimuit. Just get that tri top or tri suit.

Carry the right food

You don't want to carry too much or too little food. Carry too much and those  energy bars you packed in the morning feel like gold bars during the run. I prefer raisins and dates, easy to grab and eat.

Throw away that water bottle

Get a sipper bottle, that way you don't have to struggle with unscrewing/screwing the cap or worry about spilling the contents while your trying to cycle.

Learn freestyle

Because it's faster and takes up less space so you can navigate the crowd efficiently.

Chappals

Keep a pair near your swim exit, the walk/run from the quarry to the transition area is painful, you might step on a thorn or two and the area is pretty rocky.

Learn the route

If you can't do a test run before the day of the race make sure you memorize the route. The signs are pretty easy to miss and confusing at times and in certain parts of the race there are no signs at all.

Sunscreen

Do I have to even explain why? Lacto Calamine has these tiny tubes of sunscreen which can fit into your pocket so no reason why you can't carry one while you race.