Stay away from credit cards. Ive had them, used them correctly, yet there is no need for them. All a credit score is is an indicator of how likely you are to give a company interest. Use cash, buy what you can afford, and stay away from credit cards. Everyone says they know how to use them and wont over use, but look at the world in general. The average household has $8k in consumer credit. Odds are people are going to use them incorrectly, thats why credit card companies are so profitable. In addition, people spend about 1/3 more then they would have using cash, because the credit card makes it so easy and there is no emotional connection swiping a card, as opposed to handing over physical cash.
I paid off and closed all my cards about 5 years ago, and never looked back. Save up some money to cover yourself for 6 months for emergencies, and you have no need for credit cards.
As far as the statement about leaving the cards open or it hurts your credit, my credit score has actually gone up over the years and is near 800. A mortgage and student loans are all I have open. Also if you have credit cards open, with a limit, even if you carry a zero balance, when being considered for loans, that available limit goes against you, because its available credit you could go max out the next day. If your worried about your credit score, that will get estabolished through cell phones, auto loans, home loans, and even through monthly utilities. Pay all of them on time, and you will estabolish credit without getting into the credit card game. As far as home loans in the future, if your credit score is low, find a mortgage lender that will manually underwrite your loan, not just look at credit score, like most big banks do. They can evaluate your debt to income ratio, your payment history and base it off of that. Save your down payment, and your good to go. Don't open yourself up to that risk just to build credit.