An educational  TED Talk by Julian Treasure about being an effective communicator.  He takes the first principles approach, beginning with our attitude.  Some of his insights include

1. Avoid the 7 “sins” of communication – gossip, judging, negativity, complaining, excuses, lying, dogmatism.
2. Embrace the 4 “cornerstones” of effective communication – Honesty (be clear & straight), Authenticity (be yourself), Integrity (be your word), Love (wish them well)
3. Work with a voice coach on the different aspects of speech including – register, timber, prosody, pace, pitch & volume
4.  He also shares a few vocal exercises to do warm up your voice before a speech

If you are interested in improving your communication skills, there is a great platform  – Toastmasters International with clubs all over the world, that can help you hone in your communication & leadership skills. I highly recommend it.