I've only done that once, when one of our local ladies posted a pic on the board of herself in an outfit that absolutely drove me wild- asked her to wear it and she was more than happy to accommodate.
I've seen many provider websites that discuss open to that request, though some suggest you buy it if it is something they don't already have.
i am new to the hobby and was wondering what the guidelines on asking a provider to wear a certain outfit would be dont want to sound rude or demanding just certain things just look really hot and get me going easier
I don't mind at all when a client asks me to wear something special. If you've seen pics of her wearing something you'd like of course you should ask. If you haven't seen pics of an outfit you may want to ask if she has one and if not offer to bring one as a gift.
Just ask. I'm always happy to acommodate clothing requests if I can. Emphasis is on "if I can" of course. But most providers will be happy to dress per your request if she has what you are looking for in her wardrobe. If she doesn't, ask if she would mind if you brought her a little something to wear. Most ladies will be happy to model anything you bring her 
I've only done that once, when one of our local ladies posted a pic on the board of herself in an outfit that absolutely drove me wild- asked her to wear it and she was more than happy to accommodate.
I've seen many provider websites that discuss open to that request, though some suggest you buy it if it is something they don't already have.
Yes, I suggest they purchase it new for me to wear if I don't have it. Not because I 'expect' the gift but because I don't want to wear an outfit god knows how many women have worn and god knows how many times it 'has not' been washed. If he wishes to take it back with him, no problem, as long as it was new for me to wear.
When contacting here by email
ask her her limits
and write a genuine request that it turns you on
if she wore ex. A maids outfit
It's about the 'way' you write it
Be a gentleman about it
I have a little fetish for nylon stockings and most of the time the provider will be happy to wear, either some she has or some that I provide. Only once or twice have I had someone refuse...and they lost my patronage.
a particular outfit that she is shown wearing in a pic on her site. Other times I have asked a lady to wear a particular color of clothing.
I have asked providers to wear something specific, either from their website or just something I wanted them to wear. I've also had providers ask me if there is anything specific that I would want them to wear.
I'd say check their website first to see if there is anything that they are wearing there that you like, or if they say somewhere on their site that they take clothing requests. You would probably have to buy her something to wear if she doesn't own it. I don't think the ladies want to wear items of clothing that have been worn by others before.