You can also use the DeOxit on the preamp tube sockets and tube pins if you're giving the amp a good one over. Good clean contacts are a requirement for your best operation. Even Radio Smack carries spray cans of contact cleaner which will work in a pinch if that's all you can get.
However, do NOT use either of these on the power tube contacts. Those require the Pro-Gold or whatever it's called (if I wasn't so lazy I'd walk to the bench and check it out) due to the high voltage, but that is also a very good idea on older amps that could use a good cleaning...