Creativity is symbolic. Creativity is directly proportional to the source of your information. To sound credible you have to plug away whole box of thoughts you hold. In short, you have to advertise the dawn of your communication message.
Few habits that will absolutely nourish your credibility will be
Read as much as you can
Read whatever gets in your hands; let it be a piece of newspaper, a comic book, a flyer or any article running in the side of your computer screen. You never know which scoop can act as cherry on the cake. Reading will always increase your database that will help you quote different themes which will in return add on credibility stars in your communication!
Give examples for everything