Whether a person is familiar with the intricacies of typography or not, the style of type will convey subliminal communication. There are a number of factors that can contribute to that communication: the contrast and modulation of the strokes within the typeface, how the stroke terminations are shaped, and the proportions between the height and width of glyphs. If you've ever looked at a typeface and found it to feel warm and inviting or cold and mechanical without really being able to put your finger on why, it's due to the subliminal messages that typeface is conveying through these subtle details.

Pay attention to the keywords that come to mind when you view a particular typeface. Pay attention to the feelings the typeface evokes in you. Then consider that many of your users will have the same feelings that you do when viewing the typeface. Even if a typeface is supposed to be "modern" or "formal" or "whimsical," if it doesn't evoke those feelings in you, it's unlikely to do so for most others.