People will tell you all sorts of bullshit that doesn't work, or dissuade you from credit in general or crap that isn't going to help like "open a store card".
Bottom line - if you want to generate credit, you will need a revolving account. It is not easy to start because people think that any card will work. No way. You will not be approved in most cases for 90+% of the revolving credit out there. Look to "starter cards", like Capital One, Orchard Bank, Target, and Walmart store cards. Those are fairly easy to get. Apply for all your credit on the same day - as it looks like you are shopping and not searching desperately for credit. But don't go overboard. Find 3-5 cards that are rebuilder or "starter" cards, and apply for them all. Use forums such as infinitecredit.com as resources. Places like whogavemecredit.com can help a little but tend to be a little out of date with details. It never hurts to actually call one of the credit cards to apply - sometimes the phone droids can help vs the online approval.
If none of that yields yo any credit - then open a credit union checking account and wait another year. You'll be able to get a secured card through them, and in another year with your secured card at a 0 or very small balance you'll be able to get an unsecured card with them, then you'll have enough score for some un-secured credit.
You can also buy a car - in most cases if you get $2500 and buy a car for <$10,000 (which means sticker price for about $8500 (taxes/fees etc)) you'll almost always get approved even if its a huge interest rate. This secured loan is a big positive when you pay it off.