Give Them Details
A good action scene paints with a broad brush, but then zooms in and focuses on select specifics. Details make the scene feel real to the players. Landmarks, place names, and even military unit designations lend reality to the situation, not to mention keeping one fight from being just the same as the next.
Saying “good job, you eliminated 20 Atomic Supermen from group B, but another section of group B is nearby” is not as good as:
“A police officer looks up from his radio and shouts 'They need help over by the Opera House! The 32nd out of Fort Myers is getting hammered, their tanks are out of commission and we've got people trapped in the subway under the fighting. Get a move on heroes!'”
— excerpt from Day of Dr Null