Placing a witch or a vampire on your front porch is great, but by adding a few other items around him or her makes it much more believable and will really make your Halloween party guests and trick-or-treaters go, "Wow!" And, it can be done easily and relatively inexpensively.
Adding details to your Halloween yard haunt is kind of like building with building blocks. If you stack them one on top of the other, eventually they will fall over. That type of structure is not very strong. But, if you build in stages and with a broader foundation and support, your structure will be much stronger and can therefore be much taller. The same is true for creating Halloween scenes.
A simple example of this is our witch prop from our 2008 yard haunt (pictured). We built her up using a cauldron and home made cooking tri-pod, some rotting skulls, a campfire, some snakes and a frog.
A much more complex example would be our Pirate's Cove display also from our 2008 yard haunt. Here, we added a lot of detail to a small area. You can see pirate corpses, a treasure chest filled with treasure, crates and boxes on the dock, fishing nets, weapons, and a lantern. All of this adds up a much more believable scene which will just blow away your guests.