Proofread!

You'll rarely find a typo, weird formatting, or poor language in marketing materials produced by big companies, because they usually take the time to have several people review whatever they send out to make sure it's perfect. Guerrillas often write their own marketing material, and it's often not possible to pay a pro to review your work. But that doesn't mean you can't get it right!

Before you send out anything, have at least two other people read it for accuracy. Any time you spend making your copy perfect is worth it, because it makes the difference between looking like a pro and looking like an amateur.