If, like me, you find yourself programming in Lua just infrequently enough to not be able to remember various bits and pieces, this site has two PDFs you can choose from to print your own quick reference guide.
The page ordering won't be perfect, but my suggestion is to print "luarefv51.pdf" double-sided (for a total of two sheets of paper), cut a notch between the two logical pages on each sheet and then get them both laminated with the thinner laminate. Fold down the notch and you've got yourself a really nice little quick reference.
Don't believe me? Look closely at the full-color laminated reference cards next time you pass a shop with them. That's how they're made.