Stop the trimmer. Take your fingers off the operating trigger and turn off the power switch. Unplug the power cord before attempting to free the blades.
Inspect the blades and determine the cause of the jam. Grasp branches jammed between blade teeth and bend the outer section back toward the stem. Clean breaks usually free the machine. Clip the trimmer free with pruning shears if the branch doesn't break. Shear any broken wood clean with the pruning clippers.
Place the trimmer on the ground or a flat work surface and check for damage and lodged debris. Push out wooden debris stuck between teeth with a small wooden dowel 3/8 or 1/2 inch in diameter. Wear gloves and be careful--a slip could send fingers into the cutting teeth.
Check for bent teeth or cracked blades, either of which could cause more damage to the trimmer. Replace damaged hedge trimmer blades before using the electric hedge trimmer again. Sharpen dull blades to improve the trimmer's performance and prevent more serious issues.
Prevent blade jams by keeping the cutting blades in good condition. Clean blades after use--plain soap and water rubbed over the blades with a clean cloth removes most dirt and sap buildup. Resin removers clear the blades of sticky evergreen sap.
Spray the hedge trimmer blades with oil or WD-40 after cleaning. Regular lubrication increases efficiency and prolongs machine life.