Everyone has given great advice.
In addition to all that, you should focus on your emotions and feelings. Remember, emotions are our friends. Whenever you feel like you should act a certain way or do a certain thing, ask yourself how you're feeling. If you're feeling great that means you should go ahead and do it. If you're feeling lousy, meaning your emotional guidance system's telling you that what you're about to do or are doing is not something that you want and is in alignment with your higher self.
More you do things that do not make you feel good, more you'll feel like crap and the lower your self esteem will become.
More you do things that make you feel happy and joyous, higher your self esteem will be.
So, if you're amongst a group of people and someone tells a joke and you start laughing but you realize that you're not laughing because it's a funny joke, you're laughing because everyone else is laughing, therefore you're not being true to yourself. So, you're giving your subconscious mind instructions in a way that it doesn't matter what you feel about a certain thing, you have to do things in order to please others.
Laugh if you feel like laughing. Don't if you don't. Be true to yourself.
Listen to your emotions. They're your best friends.
If something makes you feel good then keep doing it and the more you do this, happier you will be and higher your self esteem will be.
That's also why noticing all the good things that are in your life matter so much since they make you feel good.