Develop a clear concise message. Limit your promotion to a single product or selling point.
Colors
Use a dark background contrasted with light text.
Fonts
Keep fonts simple, sizes and styles clean. Thin or script fonts can be hard to read, as can fonts that have too much contrast of thick and thin. Mixed upper and lower case is easier to read than all caps.
Style
Avoid special effects. Beveled edges and textures may be distracting and often appear blurry.
Text
Limit copy to 25 words. Use short phrases that the reader will remember.