Actually carrying a balance is good for your credit.  But keep it very very small so you dont pay much of a finance charge.  Remember that the CC companies dont make any money if you dont carry a balance, and therefore are not likely to open up larger lines of credit with you. 

On balances on credit cards.  You will take a credit score hit if you exceed (dont qoute me cause I'm 2nd guessing in my head) 50% or is it 60% of your open credit line. 

Cole, they will not open up your credit huge on one phone call.  If you have $2500 now, they may go to $4000,  then after 6 months you may get them to $6k, and so on. 

My suggestion would be to get an American Express, and use it for everything.  AmEx does not allow you to carry a balance it must be paid in full every month.  You earn points this way.  My wife and I took a 1 week vacation in California last year 90% paid for with AmEx points (flight, rental car, and hotels).  This year we flew to and from Europe, and had 4 nights in a Hilton in Paris covered with points.  What do we do to get such points?  I run everything I do across my AmEx.  I mean everything, except for places that dont take AmEx, and then I scoff at them!  ****ers. 

Credit cards can be good to build credit, you just have to know yourself, and not think you can splurge just cause you have the open credit line.