* Not a teacher
1. It's nice talking to you.
2. I bought a new car and its color is blue.
3. It makes me happy.
4. Why did you bring me the spoon? I don't need it.
5. Never mind, it's OK!
it's = abbreviation for it is
it = pronoun, 3rd person, singular
I don't think anyone is willing to provide (or can provide) all the possibilities and contexts in which you can use it or it's. Just give us contexts (like you did) and we will help you to fill in the right form. If you need further explanation like "why did you choose "it" and not "it's", do not hesitate to ask.
Student or Learner