Pick up some rug grip from a local retailer. This material is rubbery and, when placed under a rug, prevents it from slipping. If the rug is too large you can use multiple pieces of rug grip.
Cut the rug grip to better accommodate oddly shaped rugs, such as bear skins. You can cut the grip rather easily with a pair of sharp scissors.
Sweep away any dirt or hair that may be on the floor. It is easy for the debris to stick to the rug grip once it is placed on the hardwood floor.
Place the rug grip onto the location of the floor where you want the throw rug to be.
Lay the rug onto the rug grip and you are all set. You now have a throw rug on your hardwood floor and it isn't going to slip when someone walks on it.