Speak in front of a mirror on any topic you like ( may be introduce yourself in 2 min etc).
Be conscious of your TONE.
Make sure that you practise prosody by emphasizing the points at the right time.
Your speech should be full of peaks and valleys of your voice.
Do not emphasize repeteatedly in the same way otherwise its effect will be lost.
Do note down the positive differences you notice.
Stay Conscious of this throughout the day whenever you talk.