Great reminder birdrescuer, thank you.
If you have baseboard heaters then vacuum them out, they’re usually relatively easy to open.
After changing my furnace filter I will remove all the heat registers and shove the shop-vac hose down as far as I can to remove anything that has collected during the past year, then I’ll run the fan for 10-15 mins with all the windows open.
Of course it means having to dust and vacuum the house after, but it’s well worth it when the cold weather arrives.
Another easy chore is to open and vacuum any bathroom fans too, augments better air flow.