While new credit only accounts for 10% of your FICO score, it really can't be ignored. If you're young and don't have a lengthy history, opening up a new account can hurt your score as too much credit is generally considered risky. If you have what might be construed as too many accounts, then the thought is that it's too much to keep up with, especially all those different payment dates.
Although the length of your credit history only weighs in at 15% of your score, it is still vitally important. Don't confuse this with your payment history; your payment history is the quality part, while your payment length is the quantity part.
Many seniors graduating from school already have a mortgage on their hands. I've spoken to several people who have student loans totaling over $150,000. Your best first step would be to start paying down on that student loan and start saving for a down payment.