Learn to Draw

If the reason for this is still unclear, here's an explenation from famed art director Ron Brown:

"It is an advantage to be able to draw, as it enables you to put down an idea on paper. If you understand perspective, know how light behaves, how anatomy works and how to make use of white space, it will help you do a layout. I use a Pentel to draft an ad and a computer to craft it."

and about advertising- i recommend to take a look here>>>

http://www.tonycullingham.com/recommendedreading.htm