Any sales training or management training course will teach you the importance of persuasion in negotiation. It will also strip back the ideas represented by those words so that you realise how fundamental these things are.
The fact is that negotiating is not something that is highly specialised and only occurs at certain specific times. You are negotiating on a daily basis. Some would say all the time. However far you buy into that idea, the fact is that success in negotiating, or to put it another way, getting what you want, is down to how persuasive you are.
What is persuasiveness? It is a combination of things. Certainly being charming, or having charisma will help. The most important thing though is to understand the person you are negotiating with. That is, be aware of their behavior and attitudes.
Once you understand your adversary, you will be able to decide what tactics to use. You probably do a great deal of this without even thinking about it. However, observation and self reflection will only make you more effective.
For example, some people will react well to a genuine, sincere compliment. This might make them seem shallow, but that isn’t something to concern yourself with. Sometimes flirting can work, but that needs to be handled with extreme caution.