I download all transactions from taxable account(s) into a spreadsheet and (electronically) store away that spreadsheet file on the hard drive (I find this much easier than downloading all statements). Mostly this is just me being my anal self, but it has some benefits. I can sort by type of transaction to quickly get the fee $$$ taken out for my FA (although that will no longer be deductible starting in 2018). Also, I can see all dividend receipts, as a check against the 1099s when I receive them. And of course the buys and sells make it easy to fill in Schedule D. I had trouble one year with the download directly from Fidelity, so I feel better doing Schedule D "manually".
Oh, and of course one should change the batteries on the smoke alarms, test the CO2 alarm.
Other things on my list, which I culled from various other lists found on this forum, over the years:
Put ticklers on my Gmail calendar to pay estimated taxes each quarter
Review and update retirement planning spreadsheet
Set up budget/expense tracking spreadsheet for new year
Make sure all accounts have beneficiaries and secondary beneficiaries
Download all health insurance transactions from previous year (we have expenses > 7.5% of our income)
Update letter to the kids that has all of our key financial information -- account numbers, current values, login info, etc.
Think about and if needed, update will, healthcare POA, etc.
Run a free credit check report with one of the three companies