Here are a few tips that could help you evaluate the advertising effectiveness when advertising in print media:

• Use different phone numbers on various ads or in various magazines
• Have a slightly different call to action on each ad, e.g. “Ask for a Quick Quote” or “Ask for a Free Consultation”, or “Call for a Free Audit” etc.
• Provide slightly different offer in each ad, e.g. pick a different product or slightly different price – $9.99 or $9.97

With all these options, you will have to always put down what the prospect asked about so that you can track back which ad brought in most customers.