I just learned that there is the nice Node Reference URL Widget module. Basically, it allows you to add a add a A link in the node view pages of content type B, if there is a node reference A->B. When you are viewing a B node, clicking on the add a A link would lead you to the node creation page of content type A, with the A->B field populated with the B node you were just viewing. That way the user do not need to figure out "which node B am I adding this node A to?"
Our sites mainly use Entity Reference. Is there a module that provides similar functionality for entity references?