What we as equipment managers try to do when fitting a player is make sure that the slash guard on the shoulder pad overlaps the top part of the elbow pad, and the bottom part of the elbow pad is overlapped by the cuff of the glove. There should be a gap between the shoulder pad and the joint it protects. The key regarding shoulder and elbow pads is to keep a slight gap between the actual pad and the bone it protects. This will reduce the impact of direct blows to the joint. If the pad sits right on the bone, your joint is going to absorb the full impact.
Similar rules apply for the lower half of the body, starting with the pants.
It's important to remember that the looser the pants are, the more vulnerable you are to getting injured in the hip area. So a nice, snug fit is probably best. Also make sure that the bottom of the pant shell meets with the top of the shin pad to protect the area above the knee. The hip pad, highlighted, should sit on the center of the hip bone. You want to make sure that the hip pad of your pants is in the center of your hip bone.