I’m about to run CoS again and here are my recommendations:

1. Plan things out. There are numerous spins you can put on Strahd and the storyline in general. Read the whole book and figure out what story you will be able to tell the best. Realistically, you may run 60% of the book or so; figure out the best path for you the lean the party on.

2. There are some real black and decker pecker wrecker fights in the book. Scale them with level. Bone grinder can be an easy TPK, pull back a bit there. Wizard of Wines can out resource a party that thinks they can take Wave after wave; drop progressively less subtle hints. For Baba Lysaga and Amber Temple, let loose... make them feel like the build up towards Strahd.

3. Give consistent reminders of how Strahd can and will kick their ass, but don’t over do it. Strahd should be a returning cameo not an every episode character. In that regard, you’ll likely need to empower Strahd a bit for the final showdown as he’s surprisingly easy to kill for his CR.

4. Give them time to explore in Castle Ravenloft. Half the fun is finding the story and there’s loads of it in the Castle. There’s loads of potential tension there to be had, make sure to give it time.

5. Remember CoS is about building tension (story-wise). But you can’t just build and build. Make sure you work in release valves at points where they can see things getting slightly better while realizing it’s at best only temporary.