"Good advertising" is certainly a subjective term. Different layouts, font styles, images, and copywriting styles appeal to different audiences. You can run the most visually stunning, well-written ad ever crafted, but if it's aimed at the wrong audience, it's not a good ad.
I define good advertising as that which moves a prospect or client to action. Action can be picking up the phone, visiting a retail location, or requesting additional information. For tips that will help you create ads that will be noticed and acted upon, read on.
Know as much about your audience as possible before writing or designing anything. This is elementary marketing, but it's easy to lose sight of it in the day-to-day management of your business priorities. If you're targeting the youth market, your approach and design elements will be vastly different than if you're after the 50+ crowd. And if your product is aimed at the business-to-business segment, you'll use different techniques than if you're selling to the consumer market.
Advertising is about selling. The point of your ad is to generate interest in your product or service. You are not trying to win awards, be the next Matisse, or conquer the ad world. Don't get me wrong - advertising can be visually stunning as well as effective, but don't get so caught up in the minutiae that you forget that the point is to sell.
Unless you are very capable, hire a freelance designer or agency to create your ads. With the proliferation of desktop publishing tools, many small-business owners have started creating their own ads. I strongly advise you not to do this unless you are very proficient. The reason is simple: be an expert at what you do best. Do you really have the time to keep up-to-date and educated on all the latest design software? The money you save on design fees is nominal compared with what running a bad ad costs you.
Speak clearly and concisely in your copy. Avoid buzzwords, clichés, and puns. Speak to one person, not the masses - make your ads feel personal to your intended readership. If copy isn't your bag, work with a copywriter to create the wording of your ad.
Don't go overboard with graphics. This is especially tempting if you're creating your own ads - all that clip art just crying out to be used! Graphics should enhance your advertising and help draw people into the ad, not overwhelm it.
Take the time to write a strong headline. Keeping in mind your audience, and write several headlines until you come up with a particularly compelling one. Test headlines on your friends and colleagues. Beware of overused words (although "free" is an oldie but goodie) and any humor that your audience could construe as offensive.
Pick one message and one message only. Don't try to cram everything into your advertising. Select one point, product, or offer in your ad, and build the copy and design elements around it. Ads that try to be all things to all people usually fail to reach anyone.
Consider the 40-40-20 rule. The catalog industry believes that there's a 40-40-20 mix in creating a successful catalog: 40% is offering the right product, 40% depends on the right list, and 20% is creative. Translate the list to media placement, and this formula will help you in putting together your ads.