1. Let me begin by saying that the following only applies to very, very, very few photographers (or models); unfortunately it is sometimes difficult to tell the good guys from the bad guys so you have to be cautious at ALL times and always be aware of your safety and security.

Know at least a little about who you are shooting with. Check references or email a model or two that the photographer has worked with. I now require ID -Driver's License is fine- and I am now photographing it on the advice of about everyone. If you are going to be doing anything see-thru or nude or too suggestive, and you look anywhere near 18 (I mean even some 20 to 30+ year old models), the photographer might also ask for a copy of your birth certificate. You might want to make some copies that you can leave with the photographer. Ask for the photographer's ID, too. I never object to this exchange before the shoot. It is all a matter of safety and legalities and it protects both of you. (Actually, it is a courtesy to the photographer who has more to lose than you do...like 15 years...if a mistake in age is made; and 'oops!' doesn't cut it.)
 
2. Cell Phones...your lifeline to safety. Some models arrange to make a phone call to a friend or relative on arrival and periodically after that. Don't be too light about your security. I never object to a model 'checking in' during the shoot. Never meet a new photographer and go with them to some undisclosed location without someone knowing exactly who you are with and where you are going. If it doesn't seem right, leave.
 
3. Escort (For the model's safety, one person) - It's OK to have an escort with you, but work out how the photographer handles this BEFORE showing up for the shoot. If the escort must be in the studio they should encourage the model and relax. A photo shoot becomes a creation between the model and the photographer. There is always a rapport that develops between them during the session...good, bad, or otherwise...that is shown in the photos; it doesn't matter whether it is a glamour shoot or a portrait at Wal-Mart, ANY distractions take away from that and the end result is no longer the photographer's and model's work, but a committees. Many times the model will be looking to the escort for 'approval' of how they are doing rather than to the photographer. Portfolio shoots like these are creative by nature...we don't have a storyboard or layout to follow, it is nearly 100% created on the spot. The escort is there for solely for the model's safety and not to oversee the shoot or watch the model; the model knows what she wants and her 'limits' and should have communicated those to the photographer when making the arrangements for the shoot. ANY comments/communications, verbal or otherwise, between the model and escort may end the session. The escort usually ends up in another room with a magazine.

4. Escort (As an Assistant) - This person plays a dual role, both for security and to help the model. The BEST escort is someone that can help you with hair styling and makeup and wardrobe; that person then becomes an integral part of the shoot that the photographer is used to working with. Sometimes the model will bring an MUA and/or a hair stylist.

5. Friends (non-escort) at the photo session. You've got to be joking. Absolutely not. And unless your making 7 or more figures from modeling or entertaining...NO entourages. This is a business, not a day at the mall. If you are shooting with a friend, then the two of you are probably in the studio 'together' only during shots that you are doing together....otherwise they are in the waiting room or Wendy's...We'll work this one out on a one-to-one basis.

6. A commercial shoot usually has MUAs (make-up artists), hair stylists, wardrobe assistants, the art director from the ad agency, possibly an agent from the modeling agency, and others. However, the model must have only one point of focus for approval, the photographer (or art director). Others have specific jobs and are in the background. 

7. I hope I said this right. The models safety is of foremost importance. Escorts are fine, just pick the right one and the 'mouse in the corner' is a good way of thinking of them at the shoot. -Whether the shoot is Fashion, Glamour, or Artistic, it is hard work for both photographer and model and requires concentration. This isn't a family outing. Think of the shoot as 'going to work'; fun, but work. 
(It should go without saying, but no one under 18...not even the model's children...should be in the studio area if any type of nudity or sheer clothing is being photographed.)