Where's the best place to start learning how to write dialogue?

I've read books and tips but about it but it's always about what the dialogue is about like tension, character, etc., but never about how to choose each individual word. Every time I write a scenario between two people talking, I feel as if my character's words are bland and uninteresting. That my vocabulary is not colorful enough as well as sentence structure. Even this paragraph I'm writing seems monotone and ill-formatted to me and I don't know how to fix it. I especially think I use too many words to express what I mean.

So, where's a good place to start or ways to practice creating dialogue?