The first thing credit card companies look at is how much debt you already have. If you have a high debt-to-income ratio, you are not going to get approved for the credit card. What you need to do is examine what debts you have. Pay them off, or at least pay them down to a small amount. Then apply for a credit card. In the meantime, you can begin purchasing prepaid credit cards to get online items or items you cannot pay cash for.
Next, the credit card company looks at your character. This is not your personality, but rather your financial information. They look to see how long you have been at your current job. If you have only been there six months, they probably won't accept you. If, however, you have remained with the same company for five years, you appear to the credit card company as being in a stable job. The credit card company will also examine whether you pay your bills on time. If you have a history of paying your bills late, this is going to tell the credit card company that you are likely to pay them late as well. So in order to get approved for a credit card, you should make sure that you have been paying your bills on time for at least six months. You also don't want to apply until you have been at your current job for at least one year.
Finally, credit card companies look to see if you have any collateral to fall back on in case you lose your job or fall in to financial hardship. Collateral can be a home, car or savings account. Build up a savings account. It doesn't have to be huge. Just the fact that you have one may be enough to convince a credit card company that you have collateral.
Remember that the credit card company bases their decision on all three of these things. If you are weak in one area, but strong in the other two you may have a chance at getting accepted. Still, you should try to work on all three categories before applying.