1. Good Slide Uses brief but key phrases
Balances the amount of text to white space
Uses a decent size font
High contrast between background and text color

2. Bad Slide
A bad slide fills the space with too much text, overwhelming the audience with visual information, and overwhelms the speaker because he/she tends to read from the slides instead of speaking naturally to the audience
A bad slide often has text that is too small for the audience to read, uses photos for backgrounds that obscure the text, or uses a color theme that is too dark and makes the text hard to read
A bad slide has spelling or grammatical errors. When audience members notice these kinds of errors, it tends to distract from the credibility of the speaker.