Run the tip of the pen under your faucet with the water running as hot as possible. The heat loosens the ink and encourages it to flow to the tip to produce ink on paper again. Test it by scribbling on a piece of scrap paper.
Soak a cotton ball in rubbing alcohol and coat the tip of the pen with it. Saturate the tip completely, and then dry it off with a paper towel. Alcohol loosens clogs. Repeat the process, scribbling on a piece of scrap paper in between each alcohol application.
Apply heat directly to the tip of the pen using a lighter. Light a lighter, and then place the tip of the pen directly in the flame for approximately five seconds. Use your scrap paper to scribble the pen back and forth repeatedly to see if the heat loosened the ink clot.
Tap your pen's tip on a hard surface like a table. Place a piece of paper on the table before you tap to prevent ink from getting on the surface, in case the ink begins to flow again. The force will push a clot down, allowing the ink to freely flow down to the tip.