Tl;dr: What bit of advice do you have to make the party's landing in Elturel memorable?

For some background, Descent into Avernus is my first 5e game as a DM, and the last game I ran before this was probably in 2011? It's been a minute. That said, I have made a lot of mistakes and stumbled into a lot of resources (including reddit) late in the preparation process. And now, I'm making my first attempt to proactively enlist the advice of the community here in my upcoming session.

My party will be entering Avernus next session. They ended last session upon griffonback, headed out of Candlekeep toward Traxigor. Then life hit, and the game went on hiatus for two months, so I want to make the first game back memorable, especially given the expected content of the session. First impressions and whatnot.

So, I've done a lot of reading and gathering advice here, and I've downloaded and read through a couple of supplements on dmsguild, but I'd like to ask reddit one final time before I dive in--what is your very BEST piece of advice when entering Avernus for the first time?

*Edited for clarity.