I don't really do much since I keep things updated throughout the year. My regular monthly or bimonthly "maintenance" is:

• update share totals in my spreadsheet for all investments - I have it fetch quotes, so it stays pretty accurate even if I forget to update share totals
• double check to make sure bills are being paid on time
• check FICO score and report (I use Experian app)
• review and categorize transactions in my PF app
• transfer HSA funds into my Fidelity HSA (I do this about 4x/year)

But there are a few things I do approximately yearly:

• checking all of my credit cards to make sure I have spent something on them - I don't want them getting closed from inactivity, and I have a bunch
• review yearly average spending across categories (I do this once or twice in the middle of the year too), and set goals for next year
• look at auto and home insurance premiums to decide if I should shop around - I'll be looking for both before April
• change password on important accounts
• gather estimates from my wife for taxes so I have a feel for what that should look like (I model taxes in my spreadsheet)