Unless you learn the keyboard shortcuts for Google Reader, you can not enjoy it to its fullest. These quick keyboard shortcuts save you plenty of time in your every day feed read on Google Reader.
The most common and useful ones you should know include:
o: open or close item.
t : tag an item.
e: email a page or a selection.
g: followed by the section name will take you to that section. For example - ga (all times), gs(starred items). gu (feed), gt (tagged items).
m: mark as read or unread.
v: view the source website that sent the feed.
k/j: navigate to the next/previous item.
s: toggle star.