For extreme yummy-ness, try a good dollop of cream or double cream in both the mince or vegie sauce and the bechamel (let the bechamel cool a little first), as well as mozzarella in between each layer - mmmm.

I always put a little bit of liquid from the sauce at the bottom, then the pasta, and haven't had any problems with sticking. Cholesterol poisoning, now that's a different matter...