What worked for me was from sit hold treat on floor and only say down when she is actually in the right position. Archie was brilliant at this and lay down straight away to get his treat, eventually went onto just point down and now he does from voice command only.

Bramble (baby) is completely different, no way would she go down so, tip from trainer, sit on floor, one leg out in front with knee raised and encourage puppy to follow treat under your leg - so they have to crawl and are therefore "down"!! Of course, never press down on pup. Again, don't say down unless puppy is in down. Bramble will now do it without the leg (thank goodness!!!)

Hope this makes sense!