Never used credit before, want to make my first credit purchase

I was told to buy something big. Like 100 dollars then pay it off as soon as it post to your credit card. Don't let it go month to month with a balance or you'll pay more in interest fees. But sometimes you get behind and it happens. Don't constantly use up your credit card just because. Make sure you have the money to pay it off and like I said sometimes people are in need and your credit usage becomes high. Also don't use more that 30% on your card.