Your credit score is extremely important. It can affect if you can get a large loan like a mortgage. If you are able to get one, it will affect how much you pay in interest, which could be the different between saving or spending thousands of dollars. It is vital to your financial future!
Many people don't know what goes into the credit score, or how you can improve it. One thing that impacts your score is the amount of money that you owe, and the percentage of that amount compared to your limit. In other words, your credit utilization. So, if you are able to increase your credit limit (and increase your borrowing power, it will lower your utilization, which could help your credit score.
So what can you do to increase your credit limit? The first thing is to make sure that you have a solid financial foundation and look like someone worthy of a high limit. That means you need to be someone who pays their bills on time, and hopefully has a long relationship with the creditor (so that they know you are trustworthy). If you are frequently making late payments, nobody will want to give you an increase.
Next, you should have a reason to increase your limit, and be able to state that to the creditor. When you call to ask for an increase, give them a reason for your asking for an increased limit (perhaps an upcoming vacation, or even that you know it can help your credit score), and you need to be able to tell them why they should give you a higher limit. If you have a higher income than when you first got the card, or have paid off other debts, those types of things that could help convince them to increase the limit.