Speak logically, let the other party quickly understand the idea you want to express, and improve communication efficiency. First, you must speak in an orderly manner. The best way to speak is to line up "one, two, three," so that the expression is clear and simple, and the other party can understand it well. Second, you must speak rigorously, and the words spoken can withstand scrutiny and are related to cause and effect.
I would agree but being too logical would leave a bad impression to the person that you are talking to, you don't want to sound like a robot when you are talking to someone, and you don't want someone to talk to you like that. What you need is just confidence to talk and maintaining an eye contact can be a good way to impose confidence. Your second advice sounds like something that you should do when you are being interrogated or being on the witness stand being questioned by lawyers but I do agree with that, although do not be too loose lips when talking, just get to the point and be playful.