Each font falls into one of the three categories:
Serif fonts have 'feet' at the end of each stroke, San Serif fonts do not.
Script fonts are meant to emulate cursive handwriting.
Different Appearence, Different Meaning
Be aware that each set of fonts have different associations and feelings that come with it. Does it look Modern or Old-School? Casual or Stylish? Amateur or Professional? Whatever it is you want the font to communicate, try to look at it first and think of what impression it might give off.
Use in Moderation
Be consistent and do not cramp too many styles together. As a guide, only use two typefaces on a signage - One for the Heading and another for the Body. Too many fonts may cause it to look cuttered and messy.
Make sure the sign and its intended message is readable to the audience. Size does matter in this case and you have to consider the optimal size if the distance to your readers will be a long way off.
Wherever possible, spacing should be wide. Text with close letter spacing might pose a problem when viewed from a distance.
Upper and lower case type is more effective as compared to italics, oblique or condensed.