Personally, I don't make any rules and I let auto-classification work it out. It does a good job (you can see using the Status - Internet Sessions screen in the DGL-4500). Auto-classification gives large-regular upload packets a slower priority and gives shorter, irregular packets a faster priority.
If you see something in that screen that is getting a bad priority, then you can use that information to guide the rule entry you'll make. This need is pretty rare -- it's often when trying to transmit real-time video.