There are 4 types of meetings:
1. New Biz/First meeetings
2. Presentation
3. Progress
3. Credentials
The chestnut of 'asking questions about their needs and showing them relevevent work' should have been addressed and researched by you before the meeting. If you go in blind expecting to pull examples out of a bag at random than this is unprofessional and sloppy.
You said in your first post that "I do not feel particularly professional and that I "practice what I preach", when I open my laptop in client meetings.
THAT is the issue. You have identified a problem, but do not know what the solution is. Being in the business of Design and being in Business are two different things. Most problems are easy to solve if you go right back to the route of the issue.
Maybe you should be more specific to the type of meeting you are experiencing issues with?
( Regarding Photographers - unless you are a Photographer - what has this example to with this/yor issue and the solving of it?)
An another note if you do your homework and are knowledgable you can prepare for what questions a client may ask. It is your role to sell the concept or idea and therefore to have covered all the potential bases and tangent routes before the meeting.
You mention 'slick professional experience' - that only come with preparation.
I get the feeling that you are going in blind and unprepared and that you may think that the work needs no strategy or structure to sell. If that is the case then you will always be treated as supplier rather than integral to the businesses needs. I may be wrong, please correcr me. But I firmly believe in Leading not following
Here is a blog post I did about Presentations and public speaking etc that me be useful to some people
14 point to keep your presentation skills up to scratch
http://www.love-digital.com/14-point-to-keep-your-presentation-skills-up-to-scratch/