A credit card... any credit card. Secure or not, doesn't matter (if you can get unsecured, get it). Only thing is be weary of annual fees and whatnot. Best bet is go to your bank and apply for a card.
Spend no more than 10% of your limit during the first billing cycle. Let it roll to the next cycle (your first bill should be for $0 minimum anyway). Once the next billing cycle is due, pay the balance (which should be the original balance on the card), then after the cycle date closes and charge another 10% on the card. Rinse, repeat ad infinitum.
To be honest, building credit isn't a difficult deal if you're not in a hole to begin with. If your credit history is clean, go out and get a credit card or a car loan or whatever you need, use it responsibly and pay it every month as agreed. You'll build your credit from there. There's no "magic" method to it. Just don't get in over your head with credit.