A simple tactic and shortcut is to use your personal network. Lots of people miss the fact that they have a huge number of personal and business contacts (look at your mobile phone contact list). Engage them, tell them what you do and specifically who you are looking for (local photographers). You will be surprised with how well your network can support your business growth.
NOTE - if you haven't got a lot of contacts on your phone, sit down with a sheet of paper and a pen and list everyone you know (business and personal). We often forget how many people we have met over the years.

Firstly, be flexible on time. Make sure you work around their schedules. Lunchtime can be good for short meetings. Take time to understand then specifically and think about their key motivators. What puts more dentists in front of more patients? Everyone will be very different but maximizing billed time with patients should be a big driver for most. How does what you offer help them spend more time with patients?