The cemetary for a party is considerably easier and cheaper since you don't need to purchase stone. A good suggestion would be to darken them around the edges. Look at the difference in the picture below of the aged stone compared to the non aged one. A more authenic look will be much more impressive. A big problem people have is getting them to stand up.
Nothing quite digs into the ground enough.
Shish Kebob sticks. Specifically metal ones. If you push them through the stone itself from the back at a 45 degree angle into the ground they stay well and staked for several weeks. We bought ours in a local dollar store, if you don't have one, try a Lechters kitchen store. Now you just need to haunt it.