Well, first of all be very careful and obey the four rules while handling it.
Second, make sure it's a live round so you can work with certainty. Take a pencil/pen, and gently slide it down the barrel, note how far in it goes, and then compare that to the barrel length externally (to see if the brass is empty or is indeed a live round). Don't look down the barrel.
To clear it: A number of methods exist, but sometimes simplest is best. Make sure you've got the gun pointed in a safe direction, grasp the slide firmly with one hand, and then slam the palm of your other hand into a firing grip (finger off trigger) and continue forward. Visualize this as putting your firing grip right through the handle. Typically blunt force like that will overcome any small defects in the brass that may have caused a jam. Don't hit it so hard as to overcome the strength of the hand holding the slide. Sending loaded guns twirling through the air toward the ground is typically frowned upon.