Note that I live in a heavily forested area of the PNW so not all of this may apply to you!
Where to look (casual version):
Under bridges, you’ll often find owl pellets with rodent and bird bones in them.
If you see hairy scat (poop) get a stick and break it apart, sometimes there’ll be small animal bones/bone shards. Please be safe, predator scat can have icky things like parasites.
The sides of trails. I’ve found so many bones there!
Driving pullouts that are a bit private, if you feel okay with using bones from roadkill/poached animals.
Where to look (dedicated version):
A few feet to 10+ feet into the bushes past a meadows edge.
Go to the big trees, animals are drawn to them.
Check out holes in the ground.
The sides of back roads/logging type roads.
Explore the parts of the forest you haven’t been to before. Make new trails. Walk along fallen logs.
In strangely clear spots in the forest. (As I’m editing this post, i see this and realize that’s exactly how I found a skull today)
Crawl. I’ve found so many bones by just crawling around (usually looking for other things/checking stuff out).
DEER. TRAILS. They take you to less humanized areas easily.
Bones can often get spread out, but where you find one you can typically find more if you look far/ wide enough.
If you live in a foresty type place, bones are rarely bleached white. Look for browns, greens, mild whites that don’t quite look like sticks.
Skulls are often not in the same area as the rest of the bones because it’s a good food source for animals so they’ll drag the head off for themselves! (This definitely isn’t always true however).
Think about where animals would go to die, and where predators would take their kills.
You won’t always find bones! Some places just don’t have any! Some have bones that are buried.
This certainly isn’t all-encompassing and I’d welcome people in different regions to jump in with their methods :)
On using bones in witchcraft