Outdoor advertising is different than any other medium. There is no TV show before and after to cue you that it’s coming; no news stories surrounding it that will put the viewer in a certain state of mind.

You must catch viewers’ attention while they are (hopefully) focused on something else and (theoretically) moving. That means you must engage their imagination with something eye-catching and memorable.

But, as Vincent van Gogh said, “Oh, how difficult it is to be simple.” Don’t fret. We’ve got seven simple rules that will drive your message right into your audiences’ minds and get you the attention that you need.

Rule #1: Narrow to One Key Message
Your audience is mobile. They drive by as they go about their daily lives. This mobility limits the amount of time people will see your ad to a few seconds. Your message needs to be absorbed while they concentrate on driving, changing lanes, adjusting the radio and dealing with the kids.

Companies often try to include too much information. If you need to include an address, phone number, fax number, Web site, etc., outdoor advertising might not be the best medium for your goals. The most effective designs focus on a single idea. Narrow your outdoor ad to your most important and memorable product benefit.

Rule #2: Keep Your Message Simple
Too many elements confuse the viewer and dilute the message of your key benefit thereby reducing your impact. Focus on one key message and then say it in as few words as possible. As a rule of thumb, use seven words or less and no more than two design elements.

Rule #3: Use Type Large Enough to Read
Even if you narrow your message and use only a few words, you must make sure those words are large enough to be read. Remember, your audience is zipping past and has only a second or two to read your board. To witness this, take note of the billboards you see the next time you’re driving down the highway. Of the first 10, see how many have type too small to easily read.

Avoid type that is overcrowded, has large differences between ascending and descending letters, is too fine or overweight or is too ornate and difficult to read.

Rule #4: Use Contrasting Colors
Even if you aren’t an expert in color theory, you can use some simple rules to grab the viewers’ attention. Use colors that contrast in both their color and their value (level of lightness or darkness). Colors that contrast are easy to read, and can improve recall by up to 38 percent. Those with low contrast will blend together and be hard to read.

Good combinations include blue with yellow, black with any light color and white with any dark color. Poor combinations include red with black, blue with green or any colors that are similar in hue or value.

Rule #5: Step back
To simulate how your outdoor board will actually look to a passing motorist, create a viewer by cutting holes in a piece of cardboard that are the same proportion as your board. For a 10 x 20-ft. poster, cut a 2 x 7/8-in. hole. For a 14 x 48-ft. bulletin, cut a 2-7/16 x 3/4-in. hole. Print out your design on 8 1/2 x 11-in paper, tape it to the wall and stand back while holding your viewer at arm's length. Move backward or forward until your design exactly fits into the hole of your viewer. If you can’t read it, neither can the people who will be driving by your board.

You can get a copy of the Outdoor Advertising Association of America’s ADviewsm by visiting their site or calling them at (202) 833-5566.

Rule #6: Think Outside the Margins
Don’t confine yourself to the boundaries of the board. Enhance your impact by extending your design beyond the board’s physical restraints by using extensions and other three-dimensional elements. If you sell fishing poles, for example, you might have a pole extending beyond the edge of the board. There is an additional cost, but the return can be well worth the added investment.

Rule #7: Drive the Boards Before and After Placement
Never underestimate the importance of your board placement. Drive by all your board locations before and after placement. Prior to placing the media, make sure the boards are in ideal locations and inspect the boards after placement to ensure they look like they should. Do this periodically to catch any boards that might be flagging — paper or vinyl that is peeling off. Not only does this impair your message, but it also reflects poorly on the image of your company.

Creating eye-catching outdoor advertising is challenging. But, when done well, it is one of the best brand-building tools available to your company.