Wow! What a set of advice. I must have listened to this video a dozen times!
Musical theatre as we all know is a mixture of singing, dancing and ACTING! A lot of time we forget we are telling a story and embracing a different character because we are so focused on the singing and dancing when really, the reason you are singing and dancing is because the moment/character demands it. Go out and experience, see, study and observe the world. The more knowledge you have of the world and as a person, the more flavour and layers you will be able to bring to whatever role you are working on.
I often remind my students, acting is not the last thing you do or add to the character, but it should be the first. Before you even attempt to work on the song, you should have a good knowledge of what, where and why you are singing, because this will not just inform the choices you make, but the way you deliver the song/role as well. Of course, when you are in a show, the director, musical director and choreographer will help you refine those choices, but it is never their job to do the research for you. The more you can bring to the table, the more options you get to play with.
Take a look at this video and absorb all the words of wisdom and have fun exploring the world!