When I was 18 my boss told me that I'd need credit soon, that I should start by filling out applications for a store card or two, Visa, M/C & Amex. He told me that I would get turned down by most, but one or two will accept, then the rest will follow with in a year. He was 100% accurate in that. Even when I bought my first new car, I was turned down by two car brands & dealers for not enough credit, as I was leaving the last one feeling down I pasted by a dealership that I didn't notice before that had a sale on leftover new pickups. I walked in there and got a MUCH better deal from them, and I guess that they needed to get rid of those trucks, they made sure I got the loan. They too initially asked for a co-signer, I told them I didn't have anyone who would, they then dropped that and I drove home in a brand new pickup.
Most important is that once you get credit, do be careful with it, use it wisely or it will bite you in the butt and keep chewing for 7 years.
BTW, Amex is the first major card that accepted me with 0 credit, I was a 19 y/o walking around with a Amex Gold card back then, that was a rarity back then. I still keep that card.