If the card issuer isn't one I deal with regularly, I send a small test payment before any balance is due to make sure the transaction processes smoothly. Setting up payment early means I don't have to scramble to do it at the last minute, and helps me avoid delays when my bill comes due. I recommend taking similar measures if you use autopay instead.
Credit card issuers like American Express and Citi are making it easier than ever to earn and redeem points during quarantine I keep a spreadsheet in my Google Drive that lists earning rates for each card and which one to use for common purchases like gas, groceries, restaurants, etc. When I get a new card, I update the spreadsheet accordingly. That system works for me, but if you prefer a low tech option, you could simply keep a note in your wallet that tells you when to use each card, or even use blank postal stickers to write reminders on the cards themselves.