You can usually yawn and swallow to unclog blocked ears when you are coming down from high altitudes. Chewing gum the entire time you are changing altitudes helps by causing you to swallow frequently. This may prevent you from getting blocked ears in the first place.
People who always have blocked ears when flying may consider taking a decongestant about an hour before the flight leaves.
If your ears are blocked, try breathing in, then gently breathing out while holding your nostrils and mouth closed. If you do this too forcefully, you can cause ear infections by forcing bacteria into your ear canals. A perforation (hole) in your eardrum can result if you blow too hard. See barotrauma.