Good ideas so far.
Much "local knowledge" could also be impacted on just where you are talking about.
1. An inlet in Florida or NJ subject to shoaling can be seasonal and/or subject to weather events both recent or a short time ago or the entire ICW (i.e., Hurricane Sandy which changed everything for a looong time).
2. Rocks guarding specific entrances to specific coves - these are usually well covered in cruising guides, 'cuz rocks rarely move (i.e., southwestern BC and the PNW).
3. Racing is somewhat different. Many folks quite reasonably refuse to share 'cuz they want to keep improving themselves. Local knowledge helps on SF Bay; i.e., if your start is off Berkeley or NE Treasure Island upwind to the main Bay, there is a "regular" wind shift LIFT at Pt. Blount - I don't race there anymore, so I choose to share!
I moved from decades in SF to BC in 2016. I've found boaters of all kinds to be genuinely helpful All I ever did was tell them where I was planning to go, and there would be lots of help. Of course, I read the danged guides FIRST so I had a basic knowledge of what they were talking about. If YOU don't do that homework and research on your own first, you'll have no clue what they're talking about anyway!
I've been fortunate in finding new friends, many from this very forum, who have been helpful in buddy-boating to new-to-me places, and I've reciprocated when they came further north.
And then, once you've been wherever you're going, give back and share your wealth with others.