Another for those who have good eyesight..

Pull out IBM relay.
Hold relay up to a light and look through the contacts.
You should see daylight through N/O contacts.
Pick relay by hand.
Now you should see daylight through N/C contacts

If Not...Bad contact.

Now when I was young and worked for an independent company, we didn't buy a relay and replace it. My boss would give me pill bottle with 500 needle contacts and I would replace contacts by hand. Pretty easy actually on the 4 pole relays. The 12 pole (Like CS) were a bit more challenging....Needle contacts could be purchased for 10 cents a piece.

It Don't mean a thing if it aint got that swing.

Cool, Free, Johnny Smith courtesy of NPR..HERE
http://www.npr.org/ramfiles/asc/asc25.smith.asx