Hey girl! So I'm not exactly a veteran (been doing this a little over a month), but a couple responses to your posed queries:
1) Skype: plenty of models refuse to do it, and that's a really valid, reasonable choice. It's risky in a few different ways; even if you've got a lot of cyber security set up, you still run the risk of opening up that cam and seeing something scarring or unsettling (not to mention illegal; I've heard some gnarly horror stories). If you DO decide it's something you're comfortable with, MAKE THEM PAY FOR IT! You're providing an extra component to your service (c2c), going out of your way to go off-site, and taking a financial risk no matter what payment medium you use. So make them compensate you accordingly! It SHOULD cost them more than a private chat with you, because they're getting more. So considering we get 80tk/min on MFC, which translates to $4/min, you should be charging more than that. Because you and your services are 100% worth it.
2) Private chat negotiations: I honestly, just casually ask guys what they're into, ask if they've got specific preferences (e.g. "you're into rough boob play, ok, cool. what angles would you like? do you want to be on top of my or underneath me?" "do you like a meek subservient sub or a power bottom who's gonna fight back against you?") Think of it as BDSM negotiation. It's totally reasonable to wanna know what someone wants, before giving it to them, right? Just be matter-of-fact, and it never hurts to be a little coy on top of it ;-)
3) PMs - you can change your settings (go to options when you're on the modelweb page) so that you only accept PMs from certain categories of member. I strongly suggest at least setting it so that the lowest level to send you PMs are premium members (remember, Basic and Guest can't tip, so why give them time if they're not even equipped, let alone prepared to give you $ for your time and effort). I've actually gone a step further so that only models and friends can PM me. So if you haven't tipped to be added to my friend list, I can't even accept PMs from you. It's less overwhelming, and I can focus my energy on the public chat, which is way more important most of the time. By the same token, I strongly suggest muting basics and guests. They're typically the ones who will make the most requests, unwelcome comments, etc, and again: if they can't even tip for their asinine comments/requests, why should you indulge them?
Those are my two cents. Hope it's helpful! Have an amazing time, and always remember what you and your time are worth!!