I found an article today that describes four lazy ways to improve your credit. The ideas are pretty good.
The first is to let your credit accounts age. This makes sense, but if you're not paying on time, etc., then old accounts will do you no good. That said, letting your accounts age is a good idea. A history of payments can only help your score.
The second is to stop applying for new credit. This makes sense as well. Each time you apply for a credit card or other credit, a hard pull hits your credit report. This can drive your score down quickly, especially if you are applying for credit from multiple sources.
The third is to get someone with good credit to put you on their credit cards as an approved user. This is simply a bad idea. While a friend with a good credit score can help improve yours, you have no control over that person's credit habits. Riding someone's coattails is only as smart of a plan as the person whose coattails you choose to ride. Caveat emptor.
The final bit of advice was to set your bills to auto-pay with your bank. A regular payment history that includes timely payments is a huge boost to your credit score.