The scoring system wants to see that you maintain a variety of credit accounts. It also wants to see that you have 3 revolving credit lines. If you do not have three active credit cards, you might want to open some (but keep in mind that if you do, you will need to wait some time before rescoring). If you have poor credit and are not approved for a typical credit card, you might want to set up a "secured credit card" account. This means that you will have to make a deposit that is equal or more than your limit, which guarantees the bank that you will repay the loan. It's an excellent way to establish credit. Examples of an installment loan would be a car loan, or it could be for furniture or a major appliance. In addition to the above, having a mortgage listed will bring your score even higher.
Of course, the real trick is that you need to know where to go to get one of these cards and this may take some work. The problem is that these cards are marketed almost exclusively via email, telemarketing and direct mail. This is so they can make almost irresistible offers such as “$5000 credit cards – guaranteed! ..no credit check, … no co-signer … you cannot be turned down … everyone approved,” etc.
I wanted to raise my score a nudge, so I decided to get a car loan at a very low rate. I spent a year paying it off just to get a mix in my credit. At first, my score went down a little, but after about six months, my score started increasing. Your credit mix is only 10% of your FICO score, but sometimes that little bit can bump you up from good credit to excellent credit.
If you have missed payments, get current and stay current: the longer you pay your bills on time after being late, the more your FICO Scores should increase. Older credit problems count for less, so poor credit performance won't haunt you forever. The impact of past credit problems on your FICO Scores fades as time passes and as recent good payment patterns show up on your credit report. And good FICO Scores weigh any credit problems against the positive information that says you're managing your credit well.