When your content is message-based, you must always retain a focus on the salient points. Promote only the core message of your content and you will create more impact.
Don’t mix messages — try to keep things clear and clean. It may be tempting to add lots of detail, but the likelihood of it being seen or recalled is low.
If you have a choice or influence, try to reduce any outside interference from other zones on the canvas such as the network’s brand. Consider branding the physical enclosure of the screen — why waste valuable dynamic space on static content?

Digital signage content is inherently more flexible and eye-catching because we have the benefit of a timeline — but this doesn’t mean you have to be the next Spielberg. Remember, static posters and their associated design methods have worked for decades, so despite their inherent lack of flexibility the formula for communication is well proven. Make sure that the core message is present for more than 90 percent of the timeline. This minimizes the chance that a cursory glance will reveal nothing but vague imagery.

This may be controversial, but I believe that tickers are not a good method of communication. Out of home media is not a passive environment like TV - the audience is rarely sitting still and focused on the screens. A ticker provides a simple way to squeeze lots of text into a small space. The consequence of this approach is that the content can’t be read in one glance. Get your message right and you should have no need for ticker effects, including those used on large format text. Tickers have their place. They’re fine for content that your audience would expect to consume in this format such as travel information, stock updates and news headlines.

Use motion to capture attention and draw the eye in — but don't over do it. The eye is most attracted by the onset of motion and changes in luminance. Content that includes these effects is, therefore, typically more effective at capturing your audiences’ eye. Contrary to popular opinion, however, the appearance of objects is not as effective. Too much constant binary activity, such as flickering and blinking, does not help readability and is more easily filtered by the brain.

Audio can be very effective at capturing attention. It’s much harder for your audience to filter out in a visually busy environment. The same rules apply as per motion — capture attention with changes, not continuous white noise. Bear in mind the negative effect audio can have on people who have to endure it for long periods.

Use imagery in support of your core messages. Capitalize and leverage the dollars spent on multi-channel campaigns by using the same style and imagery. Support your copy - telling people to send an SMS? Show a phone.

Select fonts that are easy to read without compromising the brand. In short-throw viewing environments, words that comprise initial capital letters followed by lower-case letters can be read faster than words that employ all upper-case letters. A general rule taken from the traditional signage industry is that that text one inch high can be seen from up to 25 feet away. Maximum impact is attained much closer, however.
Consider your target screen size and the pixel pitch to work out the ideal point size required. It may mean rendering different content versions for different screen/viewing environments.

Give people a reason to look. They’re doing you the favor. Your content needs to be stimulating in some way. It can be entertaining, informative, good looking or humorous and preferably a combination. If you get it right, you have the potential to repurpose for other marketing channels — why be the poor cousin when you could be the innovator?

Ensure that there is significant contrast between your core message and the background. Amongst others, white on yellow does not work, especially in high ambient light environments. Consider using drop-shadows or other outline methods where print based brand guidelines dictates difficult combinations.

Choose content formats that work best on the target platform. Take advantage of any proprietary facilities available to you such as data integration, content management and dynamic rendering. Avoid formats that are not well supported, as they will only cause headaches in the long run.