They usually have something to do with my depth, air, time, and where my buddy is. How deep am I, how much air do I have left and how much time is that really given the depth I’m at, how long have we been diving vs how long we expect to dive for, and where is my buddy? They should be close to me. I also adjust the knob on my reg once at depth to adjust breathing effort. When I get to surface I close it to prevent freeflow when I let go of it. I check which direction we are headed in and check the bearings and headings on compass in case we get separated or lost.
Other things are related to my camera. While diving, I check to ensure my vacuum light is green which confirms the housing is not compromised. I also ensure my flood alarm is not going off.
Post-dive, I remember to share depth and time so the dayboat or liveaboard can plan surface intervals. I jot down notes about the dive. I prepare my camera for the next dive - strobe batteries, camera batteries, o-rings, lights, etc.