Let's start with what you already mentioned. While you may have a Yellow Pages ad, it may be time to update it. What does it say; do the graphic elements and language look and sound dated? Was it designed and written for you by the Yellow Pages company or by a professional graphic designer and copywriter?
Your company should also be purchasing enhanced online Yellow Pages listings, as that helps to rank your website better when someone is searching for legal help via Google or Yahoo using keywords.
Next, just because you have a website does not mean it's doing its job. I can't tell you how many folks are losing business because their primary sales tool--their website--stinks! Great sites are designed, built and coded correctly. Not only are they visually engaging, they are intuitive, user-friendly and have been written by a professional web copywriter with SEO experience. If it's been years since anyone did anything on your site, chances are it's in dire need of an overhaul.
The investment on this is a no brainer:
A great website is SO important because online is where it's at! People of all ages are searching for information, products and services online. A great site can support your expertise and drive sales to your firm. An outdated or poorly designed and written site undermines everyone's efforts.
Since you mentioned there are no restrictions on networking, I'd suggest getting to as many meetings as you can within the geographic area where you want to get business. Also, I hope you have a professionally designed brochure that cross sells all the areas of law that your firm handles.
Another great sales tool is to give free workshops. You can also send a free white paper (a report) to those who request more information about a particular topic. Consider attending as many social, charitable and civic fundraisers as possible. People do business with people they trust, and face-to-face meetings of any kind can help facilitate interaction that leads to real trust and terrific business relationships.
Best of luck,