Google Reader shortcuts know how much

g then t: Select tags

Tags can be used to classify subscriptions, although Google Reader tags appear as folders, but actually a subscription can be marked with multiple tags, so in addition to classifying by content, you can also create some tags to distinguish their importance, improve reading efficiency. Pressing g and then t will give you a list of all labels, then select them with the up and down keys, or filter them by entering the label name.