A super easy way to teach the concept, "Drop the 'e' and add -ing." Or, "If the word ends in vowel+consonant, double to consonant and add -ing". Skip the messy whiteboards, the erasing and rewriting. Just flip a tab and move on.
***Tips*** You must print double sided and make sure "flip long side" is selected on your printer for this to work properly. Cut along the dotted lines and fold!