1. Become an authorized user
If you know a relative or friend who has a good credit score, consider asking to be added to one of their accounts as an "authorized user". Since you are added to their account, you will benefit from their continued responsible credit card use. The account holder doesn't have to let you use the card - or even give you one - for your credit to improve.
Since majority of your credit score come from whether you pay your bills on time and how long you've had credit accounts open, being added as an authorized user can have a significant impact.
2. Use Kikoff's free Credit Building Service
Kikoff is a free, non-profit service that I highly recommend for everyone. Here's how it works:
1) Apply and get instantly approved for $500 in monthly, revolving credit from Kikoff.
2) Make purchases inside the "Kikoff Store" which features personal finance resources like Robert Kiyosaki's Rich Dad, Poor Dad.
3) Never forget to pay off your statement every month with friendly reminders from Kikoff
I love Kikoff because they have completely removed all the predatory practices of collecting interest and charging fees.
3. Apply for a Secured Credit Card
If you are finding yourself striking out at every credit card you apply for - no worries. It's really hard to get approved for an "unsecured card". Secured cards require you to pay a "security deposit" in order to be approved. The amount that you pay for your security deposit becomes the revolving credit limit on the card.
If you paid $200 for the security deposit, then you would get access to $200 every month in credit. You will get your security deposit back if you choose to close the card. (Although we recommend keeping accounts open to maximize the 15% of your score affected by the length of your credit history)