The Eastern part refers to pools found in woodlands east of the Rockies, vernal pools typical of Californai are a world unto themselves.
Step 1: What We'll Need
Some small pavers
Step 2: Find a Place
Lay out your container and sprinkle flour around it to mark where to dig. Excavated until the container sits in the hole just a little proud of the ground level, we want to avoid runoff from the lawn (with it's associated contaminates) from entering the pool. Level the pool in the hole and backfill with soil, firm the soil around the container being sure to keep an eye on the level.
Setting up the pool
Use the pavers to build steps out of the pool, we aren't building a toad trap here, and without the steps they won't be able to get out either as adults or juveniles. Now sprinkle an inch thick layer of leaf mould on the bottom, if you can collect this legally from a known pool, great, if not, just from under a tree is fine. Don't worry if it floats it will sink after a few days.
Step 3: Dress It Up
If you absolutely must add plants, go ahead but locate the pool in a spot where it gets 6+ hours of sun a day or the plants won't do well. Eventually ground covers will be planted around the pool.
Step 4: Maintainance
If you live where it freezes allow the pool to dry up during the late summer and refill with spring melt, in the south the pool can be kept filled year round.
Be sure to keep leaves from filling the pool completely and most importantly NEVER ADD FISH.
Step 5: In Conclusion
Finally here's a few pictures of creatures that have frequented one of my backyard vernal ponds.