The biggest mistake you can make is to try to recreate your old team inside the new one.
The second biggest is to assume they don't know what they're doing as well as you do.
But your question is dangerous. It risks becoming an expert in error and failure. Let's go the positive route here:
Look for their uniqueness and skill.
Join them first. A trick I use is to activate my ingroup bias. I tell myself that these are my people, my friends, my new best friends. When I insist on referring to them as my new friends in my head, I start to care more and grow more connected.
Mind you I"m a consultant, so I get to rip my connections out periodically and go somewhere else, and that kind of open-heartedness does not make easy exits, but I think it's the right thing anyway.
Advice: Use COAL (David Rock):
Curiosity - what is it like to be here? Who are we in this situation? What is this?
Openness - whatever comes next, I'm here for the adventure. We'll see.
Acceptance - Oh, that's what it is. Okay. It is what it is.
Lovingkindness - What is the kindest, best thing I can do since we're here?
You'll do amazingly well.