Any advice- or lessons learned- before a remodel?

[rainyday]

Greetings- as always, it sure is nice to have a forum for questions like this for those with personal experience. It was a huge step, but one we've planned for over three years, to take out a loan to carve out a kitchen area and bathroom from the existing dysfunctional space that makes the home inconvenient for us and likely a very difficult resale in the future should the need arise. We currently are missing both these features prospective normal homeowners would want!
The contractor has excellent references and communication, has been in our area a very long time and I looked at and talked with a couple recent clients who had additions added to their historic homes and were very satisfied. So from that standpoint I feel confident in our choice. He is willing to salvage as much of the existing trim (i.e. around the two impacted windows) and related materials as possible, etc and we have that in the scope of work.
With all that said, any words of advice? Is there anything you did that worked out really well? Is there anything you wish you had thought to do, that would have made the process go more smoothly? Thanks in advance for sharing your wisdom, and hope all of you are getting lots of work done this summer!