When I went to buy my car, the finance guy there gave me a few tips that really helped my score.
1. I was going to pay a big down payment up front. He pointed out a VERY low interest rate (1%) at the dealership and encouraged me to keep my money liquid, and build up my credit by setting a monthly payment that I could comfortably pay a bit extra on each month. (Even just paying $5-$15.00 extra makes it look like you can easily handle your bills.
2. He told me to put EVERYTHING possible on my CCs and pay it off in full each month (I know- this is a bit different from other advice here to carry over a very small amount).
3. He mentioned the idea of not opening too many CCs and try to keep them active if possible- and set up autopay so I don't forget to pay them or be late with payments.
4. He recommended doing a credit freeze to protect myself from credit fraud. Its more trouble if you are thinking about opening a new credit card or making a large purchase, (because you have to unfreeze your credit) but it adds a sense of security in this age of credit fraud.
5. He recommended checking your credit often (which I didn't do, but I am going to try to be better about.)
6. I thought about paying off a big chunk of my student loan but when I researched it, someone mentioned that having a long-held loan that you are making regular payments on is very good for your credit, so I decided to keep doing that for now. Payments are pretty low and interest rate could be worse, so it's OK.
I would say I did all this for about a year now and my credit score has really gone up. Out of three scores, one was REALLY good. I am in a MUCH better position should I decide to buy a house or condo at this point. Ive also been surprised to find out how many employers are checking credit history as an indicator of employee reliability.