There's some good stuff here. I dive solo a lot because there's no one else around. I day or night dive alone off charter boats because I don't babysit divers anymore and my wife hates night diving.
When we're diving together on our boat, one drives - one dives.
Now, that all said, we both have a pretty good idea what we're doing. She's not a gear freak like I am so I take care of her stuff, but I know our stuff inside and out. You gotta know this stuff too - there's no shortcuts on equipment prep and maintenance.
Now, you also have to know to realize when you're screwing up underwater and what to do about it. Sometimes I rush things to get in the water and I don't feel quite comfortable with things - except I'm now in 120' of water. Just take a few minutes to sort your stuff out, seat the mask a little better, cinch, tug or loosen whatever it is that needs a tweak, neutral yourself out, and then get on with your dive.
This all comes with time, practice and a little common sense. Just make sure when you log your dives - something that I am horrible lax at after all these years - that your descents equal your ascents. Other than that, it's a piece of cake.