Go in knowing what you want to hear as an end result and don't think too much about how to get there.
Try to communicate your desires in straight forward ways using other songs as reference points. "We want this song to have a Pink Floyd feel like in the song 'Us and Them' - languid and spacious" or "We want a good old hard rock sound like Zeppelin gets with 'Black Dog' or 'Rock and Roll'". The engineer should have an idea of what gear and what methods to use based on your ability to explain what you want to sound like.
Have your gear in good working order - make sure your instruments are all set up and as noise-free as possible.
Get the drummer to tune his kit - or have it tuned.
No buzzy amps or crackly cords or faulty pots. I guess that falls under making sure your gear is in good working order.
Focus on what you want to hear and not how to do things logistically. DI's, Preamps, Mics - let the pros do that.
Relax and have fun! Enjoy the experience and be open-minded. Focus on getting your parts right when the tape is rolling but don't obsess. If you find yourselves getting stressed - take a breather and get de-stressed.
Good luck!
PS - I noticed your tagline reads, "hiding in plain sight" - I did a 'logo-ish' idea based on that phrase a while ago -
Check it out