On most flyers, you'll have a headline meant to catch the attention of anyone who sees it. Finding the right font for the headline is crucial. In general, you want a font that will stand out — perhaps even catch the eye of a passerby without them even needing to read the words. If you choose to go with a decorative font, the first step is to make sure that the typeface matches the message of your flyer. Many decorative fonts are general purpose but you wouldn't want to use a winter-themed font for a flyer related to baseball.
A shortcut for finding a decorative font may be to use any typeface used in your business' or organization's logo. You've already spent time showing that logo to your clients and customers, through business cards and other marketing materials, so using it in a flyer can help readers associate the flyer with your business.
It's worthwhile to print out test copies of your flyer with several different font options. You can run an informal test on how they look from across the room and get a better idea of which options will be easier for someone to read, as well as which fonts are more noticeable.