People are becoming more creative with ring bearers. One trend as of late is having a pet (usually a dog) be the ring bearer. If your dog is well behaved, comfortable with people and strange environments, this may not be that difficult at all. Where ever you're getting married, though, ask first to see if pet's are allowed. Some places (particularly churches) may not allow pets at all, or may require a little convincing. Some places may have restrictions on how close the dog may come to food as well.

Plan on having someone else to take responsibility for the dog, so the bride and groom can concentrate on everything else, especially just before the wedding. Unless you know your dog is an absolute professional or something, you'll probably want to have someone guide him or her down the aisle on a leash. This is a good opportunity to give a little responsibility to a younger person. Make sure the rings are fastened to the pillow with something like a twist tie. Consider using a fake ring while the groom hide's a ring or something if you're worried about it falling off. That's something you want to avoid at all costs.

Whatever material the aisle is going to be on, try having the dog walk on that several times before hand. If it's a strange material to them, they may want to walk around it or something. Having treats at regular intervals to the end should aid greatly getting them used to it. Your dog will be real happy being such an integral part of the new family from the very beginning!