Avoid muggle-infested areas. Some boxers won't risk retrieving it and then it becomes a wasted trip for them. Other boxers won't wait until the coast is clear and then the box is noticed by muggles, and sometimes vandals.

Avoid highly groomed areas. Even if you think it is well hidden, someone with hedge trimmers or a rake may see it and consider it trash.

Avoid rotting stumps and logs. I planted in a 6 foot tall rotting stump that became a pile of dirt in less than a year. That made the clue useless.

Hide it well but make it look as natural as possible. A pile of sticks may hide it from view, but an obviously man-made pile can attract a curious muggle.

Lastly consider protection from the elements. If it rains, will this spot provide adequate shelter?

I hope that helps.

Avoid rotting stumps and logs. I planted in a 6 foot tall rotting stump that became a pile of dirt in less than a year. That made the clue useless.

That means that rotting stumps are useless for landmarks too. Northern Utah (where I box) is dry enough that these things stick around for years, while other places (apparently) will go away quickly.

Lots of good things to keep in mind! Thanks all!