you'd list some of your preferences (young/MILF, tall/short, slender/curvy, busty/bootyish, blond/brunette/redhead, etc.).  My view is that a big part of the experience is being with someone YOU find quite attractive.

If you're experienced with sex but just new to hobbying, then you should just pick the provider who's physical type is closest to your perfect fantasy. You'll get so turned on the moment you see her that you'll have an amazing time and you'll be hooked.

If you're a bit sexually inexperienced then I think there are other considerations. You should consider one of the slightly older (30-35) providers and book 90 minutes if you can to take off the pressure.

Also, read the reviews and see if you find a style that suits you. Some providers are extremely energetic – you can pound them from behind while they grab the sheets and moan. That sort of thing. Others are more sensual and take things at a more moderate pace. Some are more submissive and like you to take the lead. Others are assertive and will almost push you around. You have to think about what you would like, then you can read the reviews to find someone who suits that style. It's not really a one-size-fits-all pursuit. All that being said, it's hard to really go wrong if you choose a provider with many good reviews. You'll learn from experience.