To use debit card, all you have to do is to know how roughly how much money you have. You have to know this even if you have a credit card, otherwise you risk not being afford to pay it off.
The danger with having a credit card is that you have an option to not pay it off. With debit cards, it's impossible. You can overdraft a little if you're tricky, but that's about it - whereas with a credit card you can end up going negative and finding it difficult to get back to black (whether because of your own faults or external circumstances).
I compared a credit card to straight razor because both are useful and safe in skilled hands, but create danger of hurting yourself if you're unskilled - a danger that doesn't exist with safety razors / debit cards.