Advertising may be used to motivate people to contact you and/or to increase your visibility - so when people meet you (or get referred to you) they may already feel more connected to you because of their prior exposure.
Here are some fators to consider:
1. Make sure your advertising dollars are invested in communicating with your targets. Every dollar spent on reaching out to a non-prospect is a waste.
2. Be clear on what you want to accomplish. Many people spend advertising dollars with a message that simply says that their businesses exist. For that kind of advertising, a prospect has to have a need. When a need matches a service, you might get a response.
But you may have a service where there is no immediate perceived need. For example, you may be a CPA and your prospects already have a CPA. You may offer superior services, but you will never get the attention of your prospect because the don't perceive the need. In that case, your advertising should quickly explain what your prospects should be enjoying.
If your goal is to motivate your prospect to contact you, you need to provide a compelling reason. For example, you might want to invite them to a seminar or offer a free booklet with valuable information.
Advertising is a complicated and expensive endeavor and you should investigate using the services of an agency. Any reputable agency should be capable of explaining how the advertising they propose is going to accomplish your goals.