By their very nature, paper bags don't have the greatest handles, but Instructable user Berkana provides instructions for some simple origami to add a quick-use handle to nearly any paper bag.
It only takes three folds to get the job done and once it's complete, you won't have to roll up the top of your take-out or lunch bags anymore. It's surprisingly secure too, so you don't need to worry about the fold breaking and your lunch spilling everywhere. You can find the whole three-step process over on Instructables.
Practical Origami: instant handles for paper bags [Instructables]