some of the hides get really tricky too! We found one that was hidden inside a large metal gate post. You had to remove the top cap of the post and the cache was dangling from a wire attached to the inside of the cap.
Another was sitting next to a park bench made from treated lumber and the cache was inside a hollowed out 4x4 post that looked exactly like the posts for the bench. I swear I looked and looked and looked, finaly touched all the posts and that one moved, otherwise would have never found it!
Best advice is to look for anything that does not belong or looks disturbed, use all your senses and you will find most of what you seek