Dear Farah Maher,
Go to youtube and type in the search bar " Patricia fripp "
Lister to her clips and videos, learn as much as you can, I am sure you will thank me for this.
My ultimate advice is to follow TED Talks... You will find the known and unknown, fields of various interests, styles of speeches to meet every character type, and methods of relaying practical knowledge in the most subtle and modern ways.
Best of luck & enjoy
par
Mohamed Jalaly , Data Center Sites Management , Saudi Aramco
Listen to some Obama2008 speeches. Also watch some steve jobs product releases. Listen to Adolf Hitler to learn how to play on emotions. Also randomly search for best speeches online, you might come across some rare, un-famous, but beautiful speeches.
All the best