Credit/Credit Cards are honestly the most evil things out there. They make money on you by hoping you forget to pay them and charging you late fees.
That being said, I have risen from very bad credit to a slightly better than average credit in a few years. This is how I did it.
Find a company you trust, and get a card through them. Get one with no yearly cost, as those are usually not worth it. If you have bad credit, your only options may be cards with no rewards system. My first card was through Capitol One, and it had a $500 limit and no rewards.
The key here is keeping an eye on your limit. I never use a credit card for what its meant to be used for (buying things when I don't have them money available, but I assume I will.), I only spend the money I already have. If I have $300 in the bank, I don't spend $400 on the card, assuming I will find that last $100. Only spend what you have.
This may not be the best way to do it, but I pay off my card every month. I dont know exactly how the effects your credit, but it will prevent interest from gaining. Paying just the minimum is how things generally snowball out of control.
Keep up regular payments and never maxing out your credit, and then in a few months you can request a credit line increase, and get that $500 to $1000, and even higher.
Another way of gaining credit is buying some stuff, and financing it. It will require you to take out a loan, and that itself will ding your credit, but paying that off regularly will raise your credit. I recently bought furniture that I could have payed off in a day, but instead I got a loan on it with no interest for 1 year, then I did the math and pay off exactly what is needed month by month to pay it off in 1 year.
This is how I did it, but I had no help/education on the subject. If I am wrong on any of this, please someone correct me and don't let this person make one of my mistakes