Kudos to Tom - he's on the right track. Indeed, Yelp is likely to have low conversions, as is AdWords. AdWords is incredibly competitive for the kinds of services you're talking about, unless perhaps, you offer web design services for a very specific niche and/or you geo-target the ad and happen to be in an area with fewer competing agencies.

I like Tom's idea to focus on marketplaces where designers compete for jobs. More and more jobs are sourced that way, so it's a great place to be seen by potential buyers who are likely pretty far down the buying funnel. Those sites didn't exist when I started doing web design eons ago, so if Tom has experience with those he'd be a great guy for you to talk to.

A couple of things to keep in mind regardless of whom you speak with:

* The great thing about online advertising is that you can test your ideas at very low cost and find out if a particular network will work for you. The trick is knowing whether it's the network that's the issue, or your construction of the ads. A little professional advice will go a long way here in helping you get on the right track.

* Finding a "hook" the draws prospects in is critical to all companies, but ESPECIALLY important in a very competitive industry like yours. How are you different from other web designers - what makes you unique? Spending some time nailing this down before you start advertising will greatly improve your odds of success.

Good luck!

P.S. If you haven't already claimed your Google Places Page (often one of the most prominent areas of the search results page on Google), do that first. Improving the experience of prospects who already know to search for your business name is the oft-overlooked low hanging fruit of increasing leads to your business.