Don't make lines smaller. Don't make bulleted items more than one line. The purpose of the slides is to reinforce what you are saying, not to say it for you. Make a script if you think you need one. Using a script makes it more difficult to make eye contact with your audience.
Eye contact is important for two reasons.
First, it makes your story more compelling and thus holds your audience's interest better. Second, and perhaps more important, you can get a sense for how the audience is reacting. That way you can go back to basics and emphasize your main point if everyone looks lost, or pick up the pace a bit if everyone looks bored. Using a script makes your message seem less personal. After all, couldn't anyone have given your talk once the script was available.