The easiest and best way to collect client feedback is to use an online service like Birdeye or Podium. Theses services aren’t inexpensive, but neither is paid advertising or other ineffective means of marketing your practice.
The best way to market yourself is to build trust, and prove that you’re trustworthy. Having existing clients write public reviews that appear on Google, Facebook or Avvo is the best way to prove your case.
If you look at the reviews you’re collecting as an investment that pays ongoing dividends you’ll appreciate why online reviews are better than the ongoing expense of advertising.