How to teach "Down"?

I never specifically taught down from stand, and only taught it from sit, but Max does it from stand about 50% of the time I would say. Try asking for a down from the standing position, and see what happens. If he does it from a stand without first going to sit, I would try using a clicker, and only reinforcing when he does the down from stand, and not if he goes to sit first. If  he doesn't, I don't have anything for you, but hopefully someone else will come along with an idea for you. 

Usually luring your dog, by pushing a treat between your dog's paws will get you a fold back down!  At least that's how I taught Dodger!  Otherwise, you can try and capture the fold back down - for instance, I know that Dodger always stretches and goes into a fold back down after a nap, so if luring wasn't working, I'd have a clicker and treats ready after naptime!
Sometimes, if you get your dog excited and in playing with a toy, you will get a fold back down naturally when you ask for a "down" because it is the fastest way for your dog to comply (and all he's thinking about is listening to you so he can get that toy!). 
If your dog already knows the "down" command, it can help to use a different word for a fold back down so they realize it is a different command altogether.
 

Crusher also just progressed to this from a sit start.  He likes down better.  For a while he was going straight to a down when asked for a sit so we had to backtrack a bit.  

When it came time to teach my pup 'down' from a standing pos, that was one of the few commands that I had a partner help me.  I had hubby facing my dog and he was collared but no lead.  I was beside my dog so he was in a heel pos.  Hubby addressed pup and said 'down, Samson' and put his hand out flat, palm down, making a downward motion.  Immed after his command I gave a very gentle pull on his collar under his chin with my right hand and ran my left hand firmly but gently down his spine, urging the down.  If he fought it, I did not push.  We attempted this several times and praised lavishly with ice cubes, carrot and zuccini stix when he complied.  Eventually all we had to do was make the hand signal and down he went.  I don't know if this helps, but it worked for me.  Good luck  Jules

I normally teach sit, then sit to down, then sit to stand.  Spend about a week working on these.  Once he has mastered them from the sit position I rarely have trouble luring the dog from a stand to a down because he already understands the concept of down.

I can't remember the method off-hand, but in Purely Positive Training Sheila Booth goes over a method to get the dog to fold into a down position from the stand. I think it involved stairs in some way. I could go check if you don't want to buy the book (although it is a great book to own). Teaching the dog how to drop into a down from a standing position rather than via a sit will definitely create a faster down, if that matters to you.
I would NOT use any kind of force to attempt a down. Many dogs find the down position to be scary, and forcing the dog into a down will just add to the stress. You want a dog who thinks DOWN is very happy place to be from day one.

If you ever want to compete in obedience then the down from the stand or fold-back down is the way to go. Actually you would learn both but it's good to start with the fold-back down so that's the default.
 
It's not hard to lure this behavior with a treat but may take several sessions. Some dogs get it right away, some don't. What you want to work on is getting the head down and the body moving backwards. You have to go gradually or the dog will just step back. With the dog in a stand, use a treat and see how far he will lower his head to follow the treat. Go down and slightly backwards. The point where he stops following the treat or moves his feet is your beginning point. Do a few reps rewarding at this point. Then move the treat just a little bit further and reward. Then a bit further. You are aiming the dog's head at a point on the ground between and just behind his front feet. Once his head is there, his elbows are on the ground. Don't worry about the butt end if it remains sticking up in the air at first. That will fade. The first time the butt goes down right after the elbows, extra rewards.
 
Just remember that if the dog starts moving or giving up, you just need to go more gradually.

I would also use a treat to lure the dog into the down, when you're trying to teach this. I had a little trouble with my dog when she was in agility and obedience. I wanted to teach her the drop on recall, and instead of sitting and lying down ( in the 'lazy' position) she could just down from a stand. The same with lying down on the table for agility. So I used a treat and had her down that way at various times througout the day, even while heeling, so that she would learn to just drop when I told her and not take the time to sit and then down. I don't see it as a problem otherwise, if the dog goes down, it doesn't really matter how he does it, unless in competiton, etc. And I use treats (graduate to the hand signal without treats)  to teach my new puppy to down, I wouldn't use force, becuase she just fights that. 

If you are being asked to physically manipulate your dog and it makes you uncomfortable, then don't do it.  You can clicker train any behavior you want by "shaping" it.
[linkhttp://www.clickertrainusa.com]www.clickertrainusa.com[/link] for some videos

I agree with spiritdog. each dog i get i am more and more using free shaping to teach. I find that if i do not mold the dog physically. they learn to think, when i move them i do it for them. they become less animated and "forget" more often.

I taught Toby "down" after he had mastered "sit". I just held the treat really low to the groun until he went "down". It was actually really easy. Took less than 10 minutes for him to "get" it.

Tobylittledude, oh my god that picture is sooooo adorable!!!!!!!!!!!!

Anyway, thanks everyone.  I got him to do a down from the stand in a day with treats!  Yay!  I just have trouble now with getting him to do the down-STAY when there are distractions around but I'm working on it!