There is some good advice, bad advice and outright wrong advice in this thread. I'm not going to pick through all of it though, no sense in arguing.
First, the outright wrong. Cell phone bills and your monthly utilities, etc DO NOT build credit. They are not loans, no one is extending you credit. They only effect your credit if you do not pay them.
The minimum credit score for an FHA loan is 620. No way around it, 620.
I don't know much about subprime mortgages though, they may loan to people in the 500's but you are going to pay for it big time. They may not even do this anymore though since the housing crash. I don't know, I own two houses but I've certainly never shopped for a subprime loan.
I worked in auto finance for years and saw people turned down all the time because of insufficient or bad credit history. I had to tell a guy with $105K a year income to get a cosigner for a $25K car because his score was in the low 500's. (I still work in finance but not consumer based)
As for the actual purpose of this thread... get a credit card. Look around for one with no or very low annual fees. Try to avoid paying them if possible. You can find cards that are geared towards building credit. Yes, the limit will be low but it matters more how you use it and manage it than how much credit you have for now. If you get a card with a $500 limit, keep the balance around $100, buy a little something each month and then pay it back down to $100. This establishes regular, on time payments and shows you can carry a card but not use it much. Also, once you establish credit and your limits rise, be careful. Always think before you buy something. Make sure it's worth paying for plus a little interest.
Good luck
