re: Improving credit score.

1.) Funnel everything through your cards unless the fee to use it is greater than the points received. It's free money.
2.) No issues with having multiple accounts open.
3.) Older the account, the better. So, don't close any old accounts.
4.) Every 6 months or so, ask for a credit increase. The higher the credit line that is not used, the higher the credit.
5.) Don't ask for too many increases in a short period of time (aside from #4). Too many hits will drop your score.
6.) Revolving debt is worse than fixed interest loans.

So, if you have a bunch of old accounts with very high unused available balances, you will have higher credit. Sure, it's gaming the system, but who doesn't. Funny thing is, once you have very high credit, you will no longer need credit because what you did to get yourself there, likely took away the need for it (barring home purchases).