Each hobbyist has different bases they want to cover and each provider has different scheduling information and precautions they want covered. In my experience, it really depends on whom you talk to.
As to the session itself or discussing specific acts, this is a red flag for me. This is why many providers request no explicit communication. There are certainly things that can be covered over the phone (location, duration, general feel of the meeting - relaxed and conversational, active, leading/following, etc), but stay away from anything you have to abbreviate (BBBJ/CIM/etc) or topping/bottoming. For first phone calls I tend to cover scheduling (date/time/duration), general feel of the session, cover any concerns/questions the hobbyist has, as well as pertinent reference information. I play a lot of it by ear, but that's kinda bare minimum. Don't drag the call out - she has plenty of things to do, and she surely gets calls from people looking for free phone sex.
Regarding clothing, I'm always amicable to suggestions on this front. I like to ensure my clients get what they're looking for, and as much as I can, I like to cover that ahead of time. Unfortunately there's a lot that I can't cover, but "I was thinking it'd be really cute if you wore a short sundress and open-toed heels with some sexy lingerie underneath" is totally acceptable. Personally, I prefer a framework like that rather than something really specific like "You should wear a black sundress with white polka-dots just above the knee and white, fishnets (SMALL webbing) and 5" black stiletto sandals." For one, like all girls, providers have things they're comfortable in. For two, if you get that specific, you'll probably just be disappointed when the provider doesn't have exactly what you're looking for. Also, in all honesty, they can probably dress themselves better than you can

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-- Modified on 11/4/2013 8:53:53 PM