When I was first bird watching on my own (maybe around 2003) I used the internet for the local mailing lists and saw that other people were seeing kinglets (I had not seen one). I read up a little on what they looked like, and then the next time I went out, I pulled over with my bicycle and saw an entire flock of them, right up close.
Prepared mind + local data is magic.
I haven't been keeping lists of what I've seen, but I've got a running list of organisms I haven't seen and want to (or sometimes stuff I got a brief look at but want more).
So this year's off season I'm trying out being a little bit more organized about writing down the list and trying to actively learn the specifics in advance.
I haven't seen all the possible sparrows for my area, but I can't keep that in focus. This is the bird search list for me:
Nighthawk
Screech owl *
Whippoorwill *
Snowy owl *
Eastern Puffin *
Snow Bunting
American Bittern
I think I've seen a puffin in flight (at a distance); I've heard a whippoorwill and a screech owl. I've legit seen a snowy owl that I found myself, but who doesn't want to see another?
Lots of people post snow bunting sightings in places where I go, but I've never seen one - no idea what I'm missing.
Last winter I hiked for miles and checked every single tree hole for a screech owl, but no dice.
For fungus my list is less well informed:
Any bird's nest fungus (Nidulariaceae)
Any stinkhorn *
Skirted Stinkhorn (Phallus duplicatus)
Stinky Squid (Pseudocolus fusiformis)
Chlorociboria sp. (Green Wood Cup and Turquoise Elfcup)
Any luminescent mushroom (Panellus stipticus?)
Diamond shaped pores: Panellus pusillus or Neofavolus sp. or Lentinus arcularius
Eyelash Cups: Scutellinia sp
Earth stars
Sprassis sp. *
The bird's nest should be easy, they keep showing up on inaturalist. My bias is clearly towards showy unusual shapes. I've seen the mycelium stains from the chlorociboria, but apparently seeing them fruit is legitimately rare?
I didn't see some of the things I had seen lots of on the previous years, this year - dry weather and spending much of October indoors. I do have a reliable spot for Sprassis, but it feels like it might be a matter of skill/interest to find more.
Plants should be more amenable to carefully timed outings:
Bear Corn (Conopholis americana)
Any Ladies' tresses (Spiranthes)
Yellow Lady's Slipper (Cypripedium parviflorum)
American Groundnut (Apios americana) *
Any carnivorous plant
Bloodroot (Sanguinaria canadensis) *
Arthropods is a little weak. I seem to be very motivated by seeing something and then wanting to know how to see it reliably?
Io Moth (Automeris io)
Toothed Somberwing (Euclidia cuspidea)
Giant leopard moth (Hypercompe scribonia) *
Cecropia Moth (Hyalophora cecropia) *
Any wasp mimicking moth - Synanthedon sp. *
Primrose Moth (Schinia florida)
Catocala Sp. *
Doubleday's Baileya Moth (Baileya doubledayi) *
Magicicada Sp.
Nigronia Sp. (2-4 year fish flies) *
I did almost travel to see cicadas a couple of years ago, and I think felt parenting guilt. For Giant leopard moths, that sighting was a success after using the "I wish I could see one" technique - Cecropia I've only seen as a caterpillar.