To Visa or Not To Visa

So I am getting my first Credit Card soon. It's a TD visa card. Now that brings up the question of to use the Visa or to not use the Visa. When do people use a credit card, when is it smart to use a debit card, or when should you just use cold hard cash. There is some sort of limit though by the fact that I will have a $500 spending limit. And the high 19.75 % interest rate is also something. Anyways these are the questions that the young have to ask.