After doing a little reading, some answers to the original question: In addition to simply gaining diving experience,
Plan every dive, even if DM/guide gives us a general plan
Practice navigating - can go snorkeling at the beach in low visibility (sandy) water and try navigate patterns.
Go swimming with one fin.
Change masks at home with eyes closed.
Eventually, practice changing air source and shutting off valves.
Etc.
Etc.
I guess another way to ask the question could have been: what are some ways to practice dive skills when not on a recreational dive? As mentioned above, it isn’t necessarily about new or different skills, it’s about being a competent diver when unexpected things happen.
Honestly, most people I’ve met here so far would think I’m nuts with all this - not about solo diving, just taking diving and skills so seriously. Most people are so lax it’s rather disturbing. I feel like I have a new story with every chartered dive. Hence, I want to be more self reliant.