https://photos.google.com/u/2/photo/AF1QipPYiPrVcTGAr954b8zovR1ucZWMzQZfdjWksuLy
For the down command, first you're going to put them on a sit. You're going to use a treat to lure them to go down but you are not going to give it to them. You need to pull down on the leash, while putting the treat near their face, then down to the ground and say their name firmly.
If the dog is a dominant dog then it may be difficult because the down command is the most submissive stance. NEVER GIVE UP! If you give up then they know they can wait longer next time, so you will give up.
You can put some pressure in the middle of their shoulder blades, while pulling down on the leash.
As soon as they are down tell them to stay. Do not say their name. Be confident that they will stay. If they get up say "NO" firmly then repeat the process until they stay for 10 seconds, then longer after.