Communication is key to anything and everything we do; being honest about how we communicate extends a part of our soul to the people we care about.
If invited to someone's home, bring something (flowers, candle, bread).
If you offer to help out, stick to your word and pitch in.
If you RSVP to an event, show up.
If you're running late, call.
If something comes up and you can't go, be mature enough to communicate this to whomever is expecting you.
If you decide you don't want to go (for whatever reason), tell the person. Honesty is the best policy; if others respond badly to the truth then there's something behind the emotion.