This may seem a bit silly, but I have having some problems quickly and efficiently determining whether a question is a comb or perm problem. I just need to practice 20-30 problems to get this down cold. Actually solving them is easy for me, just sometimes it just seems order doesn't matter, when it does, and vice-versa. I really just need some practice to get to connect for me.

Can anyone point me to a set of problems or a practice set that would help me with this?

Regards