What do all these photos have in common? They show how evil geocachers can be. Hopefully, especially for the beginner, this will take your hunting skills to the next level when you see all the ways that caches can be disguised. If you want to be evil too, you can find these and many more on eBay.
 

Underside of sand cache

That wet TP may be a hide
Mulch

Rebar cache

Fake sprinkler head
Another

And another

Fake identification number

Just leaves?

Pop bottle cap

Owl pellet cache

A robin's egg

Chain link fencepost cap
Another one

Not a hidden cache. Don't get too curious.