Let's talk about each of these objectives in turn, and I'll give you some hints and ideas on how to use humour effectively to achieve them.
Some speakers think that the best way to use humour is to tell jokes.
Some have even been told that it's good to start a speech with a joke. Because jokes take time and they are risky. A good joke takes about one or two minutes, and it's all leading up to a five-second punch line. So you'd better be telling a really good joke, and making a really good point, and expecting a really good response, to justify spending all that time on it. I've also heard people say that you should start with a joke to help overcome nerves.