Djlemma- I think she might be like myself when I did mine, and for me I was nervous due to not knowing who the photographer is. I went in and asked for the shoot without knowing what their personality was like, or if they would be the kind of photographer who didn't really socialize much with their model. They might take great pictures during it, but having someone not talking to you much/concentrating on taking the shot for a beginner is a little intimidating. Luckily, it wasn't as bad as I thought and they were extremely helpful and fun to talk to.
Now, for tips!
Before for the shoot:
*Study your character very carefully and figure out what poses would suit the character. But don't just practice the day before the shoot, practice in advance to make sure you can handle the pose so you don't walk up to the photographer with a pose you can't even keep for 2 seconds. Also, It'd be wise to make sure your photographer can do the pose beforehand like certain action shots which require fast shutter speeds. Not going to be good if the photographer has a camera like my Nikon which likes to take pictures 2-3 seconds after I press the trigger.
*If possible, see if you can talk a little with your photographer about location/any ideas you may have. I know you can do it sometimes at the location, but some photographers will have a busy schedule and it takes time away the amount you paid.
*Have more than one pose for the camera. Especially if this is say an hour long shoot.
For my tips in general for the shoot:
*Don't be intimidated by the Photographer. I had that problem as well, but once I got to meet them at the location I found that it wasn't that bad. I say we even experienced an hilarious time as bystanders kept reacting in some way or form to my cosplay. But remember that communication is a good thing to have during a shoot, why? So they can help make it the best picture for you, as well as so they know they're making you uncomfortable.
*Arrive at the shoot early by 5-10 minutes. And please, if you can't make it contact your photographer beforehand so they know you aren't coming and don't end up waiting 30+ for you to show up.
For now, that's all I can think of...but there are more, just can't think of it right now. But here was my first photo-shoot: https://www.facebook.com/media/set/?set=a.628077767203593.1073741849.585254554819248& type=3
On another note, once you're done thank the photographer and they should tell you where to find the pictures/give an estimate of when it'll be finished. Also, remember that once you do the shoot your photographer owns the rights to your pictures. Sometimes they'll hand them over to you, but it depends on the kind of contract they sign with you. So before the shoot I'd ask if you're allowed to post them online, or use them in any way.