If you want your dog's down-stay to improve, it's important that you start asking for down stays at home. A great way to practice the down stay is to have your dog practice on his or her dog bed. You really want your dog to understand that his or her dog bed is a GREAT place to stay for awhile. You can do this by rewarding your dog right on his dog bed while he is in the down position.
Another great new tool we have is the Klimb table. This is a great training tool to help your dog learn sit-stay OR down-stay. We now use these in our Basic Manners classes as well as other classes to improve our dog's understanding of "stay".
This is a Klimb Table. We LOVE them. I am now a distributor of these great tools.
When you are preparing your dog's meals have him do a down stay on his dog bed (or on his Klimb table). You can reach down and reward your dog for not getting up and you can put him back if he gets up before you say "okay". This will take some time and persistence on your part so be sure you work on this when you are in a patient mood.
Another great time and place to do this is when you are watching TV. First, put your dog on a light, indoor leash. Put your dog's bed about three feet from where you will be sitting. Ask your dog to lay down and then give him three or four treats and then tell him to stay. Then sit down on the couch. If your dog gets up (which he probably will at first), he can't really go anywhere because he's on a leash. So just put him back on the bed as soon as possible. If your dog doesn't move from the bed, get up and bring another reward to your dog and remind him to stay. You can then return to your couch and continue "watching" your show. At random intervals, if your dog is continuing to stay, you can move in and reward that good down stay. Should your dog choose to get up at anytime before you release him you must return your dog to the spot and ask him to lay back down.
Remember, the more you reinforce this behavior, the more it will happen. Make sure that you are the one that releases him even if he falls asleep while in the down position. Try building up to a 30 minute down stay.