Well, I never have professional pictures taken, so I expect my answer to be a little on the extreme here.
I have a good amateur camera, which is suppose to have quite good pixels, however it never shows, regarding of what settings I am using. I am just asking a friend to take the pics. I am giving all the directions I find appropriate, as he is really not the photograph material.
I cannot fully smile in my pics as it's really hard work to be relaxed while telling someone what to do. Also, I usually start posing and smiling and then I am waiting a little too long for the shooter, by that time my smile is forced or I'm blinking
After about 30 minutes, I have not much patience left, so if I need to change my outfits, I really need a long break in between.
Many times I was thinking I deserve better pictures but it was never the right time to do them. For a while, I was hoping I can lose some weight before I do them. Then I had some very unpleasant experiences with my hair and changed my usual blonde for colours that I cannot stand more then a month or so (dark black, vibrant red, dark purple). My hair is now quite short, as in my avatat or the pic with the short black boots on my profile, taken just 3 days ago. As I intend to let my hair grow, I don't want to invest in pics that won't show me how I plan to be in the nearest future. Of course, I can just wear a wig, I got a few nice ones but the truth is that a wig never looks natural on me and I don't want to invest in pics that make me look like a drag queen (no offence to all drag queens out there). And what happens if my professional pics with me wearing a wig look very good and they attract a lot of visitors ... who will probably be disappointed to see a short haired lady welcoming them for an appointment? Of course, I can wear a wig for the appointment too, but this is not as easy as it sounds.
Women stuff, I swear ... they are so hard. I'm normally a simple person and I think my best look is when I am natural, with plenty of light, when I smile and I laugh. I never knew how to look good in pictures and I think this comes from my childhood. I had very few pics taken when I was under 18 and in most of them I dreaded the moment. My mother will cut my fringe in a horrific way anytime she knew I have to take pics for school or for my artistic activities I was involved in at the time. For me, pics have only been horrific mementos of the times I looked my worst and this baggage is very hard to throw away now when trying to pose sexily.
If I am still escorting when my hair grows slightly longer, I will have those professional pics finally done. If it takes a bloody day to shoot them, I will make sure I have at least 6 good pics !!!