I don’t know if this is commanly known or not, it’s just that I’ve always used it and I don’t remember where I learned it.
Edit mode, when you click the RMB near a vertex that vertex (face or edge)will be selected, RMB again will unselect. By holding the shift key this will allow you to add each selected vertex (face or edge) in that highlighted group.
Anyone know if there is a way to deselect vertecies you’ve already selected using the shift+RMB method? That is a problem I often run into-selecting a vertex accidentally that I didn’t want and having to start my selection process all over again…