According to people in the know, it is best to keep a zero balance on all revolving accounts except one. On that one, you should keep a balance of between 1 and 9% of the limit. Since you have 2 cards, you should carry a small balance on one and pay the other one off in full before it reports every month. You need to use it, though, or you risk the account being closed.
Like someone else said, don't apply for any more credit or limit increases until you are ready to get approved for your new house. Hard inquiries will bring your score down for a year and will show up on your credit report for 2 years.
ETA: make sure you know your FICO score. All other credit scores can be useful in tracking your progress but useless when it comes to finding out whether you qualify for new credit.
This post was edited on 11/12 at 9:49 am