Hi!
I have same problem with Olaf, you can read about it in this thread:
http://www.dutchshepherdforum.com/viewt ... =22&t=1633.
But what I noticed over time is that he will "work" better if I play with him and make it more fun! I.E. if he just lays down and I come to him and say give him the cued for "stand" "sit" "lay" "paw" etc, he would listen, but he would give up after couple of cues or just listen after I repeat 2-3 times. BUT if play with him between cues (wrestle, cuddle, tease him etc) he would listen MUCH better, even without food.
Another example: we go to doggie school where we learn "come" command. The dogs have to come to you on the shortest way and sit in front of you. We practice first by feeding him treats while he sits in front, then moving one step back from the dog, then 3 steps etc. He is sometimes good at it, and sometime not so.
So every class you have to show your "homework" and while one man-dog team is showing others watch or practice something on their own. So, while someone else was showing, Olaf was laying down, and i watched the other team. When out turn came, i started with feeding while sitting and then moving one step a couple of times, and then moving 3 steps. It worked fine until 3 steps practice. At that point he would just pass by me and wanted to go sniff something.

Later on, while being bored a bit, I wrestled him a bit, talked to him, teased him(..) for a min or 2 and that did "come". It worked great!!
So basicaly, i can use the food to show him what i want when learning new stuff, but later on he is much more motivated by my attention and by making it fun.
And somehow, now he is more obedient in every-day-life even without me making a clown of myself all the time and without carrying smelly treats.
About choosing treats, check above link.
Does he like to play with toys? Maybe he would work for a ball etc?