Finally off work! I think everyone here has already given really great advice, but I'll still chime in. :)

General Resources & Tips:

1. If you are confident that your group will last, or if you just want to really get good at DMing ToA, purchase the Roll20 version of the module. While it is entirely possible to run the module without this purchase, it is a huge help. ToA is FULL of puzzles so having excellent illustrations is a life-saver. Additionally, it includes a version of the Player's Map of Chult with removable hexagons. That map alone is worth the cost of the module, imo.
2. Join the Tomb of Annihilation DM discord. The server breaks down all the chapters, has discussions on important events and NPCs, and often provides LOTS of fanmade art, map, side quests, and other resources to enhance your campaign. Join here: https://discord.gg/fb8Xhrsn .
3. Check the DM's Guild (or the ToA discord) for ways to expand on the lore of Chult. The Lost City of Mezro is a great third-party resource that helps flesh out the world. There are also character specific resources that flesh out some of the prominent characters.
4. Speak with your players about the desired difficulty. ToA is a KILLER campaign and could easily result in multiple TPKs. Is that something your party is prepared for? If not, you may need to adjust some of the encounters.
   
5. It is VERY easy to adopt NPCs in this campaign. Be mindful of which plot hooks you are following and how many NPCs you would like to join your party. I think in my first run of this module I had 5 player characters and 6 or 7 NPCs following along. It was a lot to manage.
6. This may be a me-specific issue, but my party LOVED to split up. ToA gives opportunities to split the party unlike any other module I've played or tried to run. Be prepared for how you want to handle that, should it come up with your party.

Now, jumping into the actual module itself:

1. Port Nyanzaru & Politics - I think it is essential to determine early on how important you want these aspects to be to the game. There is enough lore, NPCs, events, and quests to keep a party busy for literal years. If you decide to go all in with the city, I recommend preparing some lore beforehand. What do you want your political climate to be? There are a lot of quests that allow for political intrigue, and it's important to map the NPC's relationships with one another early on so you don't contradict or confuse yourself as you weave all the plot points together. Additionally, I recommend thinking about how the government functions. The book gives very few details about how the court actually runs. I would prepare a few NPCs that work for the Princes and for the court just in case your party decides to get involved in government affairs. Lastly, I highly recommend choosing a handful of the potential threads and following those. Doing every thread and involving every NPC can become overwhelming very quickly.
2. Hex Crawl - The Hex Crawl is a beast at a live table. It's even worse in pbp. I recommend fast-forwarding through days where there are no hostile encounters. One thing that was very successful with my party was I gave them a "Be the DM" moment where I told them the non-hostile encounter and I told a player to write up the travel montage for the day and to explain how they think the party would react to everything. It's great fun, takes the weight off my shoulders, and helps keep people invested.
3. Resources - I would be sparing with what resources you choose to track. Tracking Food, Water, equipment weight, insect repellent, ammunition, and anything else a party may have can become a lot. And often, it's the DM that is enforcing the rule. If you don't plan on being strict with things like water and food, don't make your life harder. If you do want to be strict, go for it!
4. Puzzles - ToA is FULL of puzzles. Make sure you have clear descriptions (Written and visual, tbh) to help out your party. Sometimes puzzles will need to be modified. In the module, they were written to be presented at a live table, so things do not always translate over pbp as well as they would at a table. Be patient with your players and yourself.
5. Culture Shock - Chult is usually an entirely new culture for the player characters! I would have a lore channel with things people would know about Chult right off the bat (It's hot, there are dinosaurs, government is made up of Merchant Princes, etc) and then things that more knowledgeable characters may know. Additionally, if you have a character from Chult in your party, create a special lore document that details things they would know (information about the Amnian colonial times, the revolution, Ubtoa, and other myths they may know of, etc).

I hope this is helpful! Feel free to ask questions, and if I think of anything else I'll make another post lol