Shift+G is goto From. It takes you to the beginning of a selected region. This is useful for marking the beginning of a clip.
Click the clip (this selects the region), hit shift+g, hit M to add marker.
In preferences > Keyboard Shortcuts, I map ctrl+shift+g to GO TO THRU. This enables me to go right to the end of a clip and add a marker the same as I do for the beginning.
Just a handy thing I like. This is kinda related to the first thing you asked about from my perspective.