There are many ways to build your credit on your own whether you have no credit or you are trying to re-establish credit. One option is taking out cash collateral towards a secured card with a reputable company that will report to the three bureaus. The Con to this is also finding a "lender" that can guarantee your collateral return after 12 months or earlier for maintaining an account with them.
Another option is companies like www.selflender.com (you can visit the site for more info on how the process works). Self Lender allows you to create a designated account like a savings or CD (certificate of deposit) to store your money monthly as if you are paying a bill but you are actually building your credit with reporting. I'm pretty sure there's a fee for doing so, nothing easy comes for free, but at least it's your own money you get back at the end of the term. I like the option of Self Lender because there is no credit score required to join and you can unlock the collateral money after a period of time + the interest it accumulated, like a savings account. It also reports to the bureaus showing that you have a trade line!
Finally, if you have the money to try this one, it may be your best and quickest option. Websites like BoostMyScore.net offer tradelines that you can buy, being sold by people who have established credit from years to decades. The prices vary, you can find what fits your budget and make it work for you! But in my experience, the only site I find reputable and have actually tried is BoostMyScore.net (and I offer the service very limited and on a smaller scale to some of my clients). More specific information is available on the site on how to buy a trade line or even sell your own established trade line.