As previous posts have stated, lighting is VERY important. I studied photography for GCSE (93% and A-Level 89%...ok you are probably thinking Boohoo... lol) and got best photographer of the school award for 3 years running(Yea, ur still probably thinking boohoo). You need to get yourself 2 light units with infrared sensors. This way, you only need to hitch up 1 to your camera and the other one will go off simultaneously. You want to get an umbrella to soften up the lighting so you dont get any harsh shaddows. There is also another apperatus which i have forgotten the name lol. Also a light meter is required with these obviously...
It also depends upon how you want to photograph her. Natural or posing. To do your homework on these, buy loads of girly magazines and u'll find millions of examples. Look at the focus, can you see the trend?
Does the photographer use standard lenses, or does the images seem softer thus suggesting a filter lens of some sort? Now you are learning.
I once did some work with a girl who asked me to photograph her for page 3. We did our research, took loads of photographs (nothing nude obviously.. would have been nice tho lol but still, some photos were good
) and came up with some really good shots. Unfortunately she didnt make it, namingly because she lied about her age and couldnt be patient, but hey thats life. (But also, admitedly we didnt do enough research and experimenting)
Things i thought worked well:
Dont just do colour photography when making a portfolio, add B+W photos too, mainly in the close ups.
when doing natural photos, the number 1 NO NO is to have the person looking at the camera and make sure the person is in focus with the background still in focus but slightly less crystal clear. (You may need photoshop for that one)
Try to get the focus on only the subject in portraits with a softening lens with a low apperture(i think thats the term) to get very little depth of field.
USE A TRIPOD... every time.
Loads of ppl will ridicule me, but i preferred canon cameras.
When doing portraits, as a previous person said, try to keep the person always in focus, that way, when the person does do a good pose, they dont need to hold it for long when you capture it.
Anyhow, i stopped photography practically all together and there are many things i have forgotten. Still PM me though if you have any questions, i might know the answer.
Hope this helps and anyone feel free to flame anything i said as i'm not a professional photographer anyway, and some things may be done better another way.