Your slides and flipcharts perform two very important roles in your presention. First, they serve as an outline for you, the speaker, as you conduct your talk. Second, they are an outline for your audience, giving them important guideposts as they move through the new information.

To ensure that your slides are effective for both you and your audience, consider these tips as you build your visuals:

Keep them clean and simple.
Use the "Six-Pack Rule" whenever possible: no more than six bullets per slide, and no more than six words per line. Also, devote about half of the slide to empty space to enhance its readability from all corners of the room.

Use high-contract colors.
High contract increases readability, so consider using white/yellow text on a dark background, or black text on a white background. Some colors are associated with specific meanings (red=lost money, yellow=caution), so make sure your words are not at odds with your color choice.

Limit the number of fonts.
Use a maximum of two to three fonts per slide, and use specific fonts sizes to indicate the type of content:
Title -- 24 to 36 points
List -- 18 to 24 points
Body Text -- 14 points or larger

Think about letter case.
Use uppercase letters sparingly, as lowercase is easer for the audience to read. Capitalize only the first word of bulleted lines of text.