ADVERTISING IS NOT an exact science. There's no precise way to measure the success of an ad campaign. You can't, for example, determine how many sales dollars are generated by each advertising dollar you spend. But there are methods that will give you a rough idea of whether or not your ads are hitting the mark.

To assess the effectiveness of your advertising campaign, you can monitor sales, new customers, requests for information, phone inquiries, retail store traffic, Web-site traffic or clickthrough rates. Use these tactics to gauge the power of your ads:

• Track retail traffic by counting the people who enter your store. Don't forget to monitor traffic before you start the ad campaign, so you'll have a basis for comparison.

• Compare sales before, during and after an ad campaign. Keep in mind that advertising often has a cumulative or delayed effect, so ad-driven sales may not materialize immediately.

• In print ads, include a coupon that customers can redeem for a discount or gift with their purchase. Code the coupons so you can determine which ad or publication generates the best results.

• Offer an incentive for customers to tell you they're responding to an ad: "Mention this ad and get a 10 percent discount on your first order."

• Use magazine response cards. Some publications offer response cards ? also known as bingo cards or inquiry cards ? that let readers request information from advertisers. You can also run your own response card in conjunction with an ad. Remember to code the cards if you place them in more than one publication.

• Use dedicated phone lines to track responses. For example, if you mention a toll-free number in your ad, assign different extensions to particular ads. Consider setting up a separate phone number for your Yellow Pages ad.

• Compare pre- and post-advertising traffic on your Web site. Your Web host logs the hits on your site and should be able to provide you with daily, weekly or monthly reports. If you maintain your own Web server, invest in software that generates easy-to-read traffic reports.

• If you advertise online, track the clickthrough rate ? the percentage of viewers who click on your banner ad. Most sites that sell ad space track clickthrough rates and can provide you with performance reports. Alternately, you could create a Web page that is only linked to from your banner ads and then monitor the traffic on that page.

• Don't overlook the tried-and-true approach: Ask all new customers how they heard about your business.

Keep in mind that you can't gauge success if you don't know what you're trying to achieve. Have you precisely identified your target audience? Read Determining the Target Audience for Your Small Business for ways to segment the audience for your marketing messages.

Make sure you have clear advertising goals. You might want to boost business overall, but your objective should be more specific: to increase sales of a new product or service, to build awareness of your company, to spur volume during a certain time period or to expand your business in a particular market. Tailor your evaluation methods to your goals.

If you're considering or running an online ad campaign, you may know that one benefit of online advertising is its quick delivery of metrics: you'll know how well your campaigns works by the clicks your online ads generate. Read What Is CPM-Based Web Advertising? for more details on one type of online marketing.

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