People out there haven't just been casual about where they bank. Many have also been extremely casual about leaving large sums in the wrong accounts -- and passing on hundreds, and occasionally thousands, of dollars of interest in the process. To get truly Foolish with your banking, you'll need to identify how much money you need to keep in typical banking accounts. The answer to this question, for Fools, should be "Not much at all." Money left in typical banking accounts (that is, savings and checking accounts) is earning very, very little in the way of interest. The average interest paid on checking and savings accounts does not even rise to the level of the rate of inflation, yet Americans today have more than a trillion dollars in such accounts.
If you leave significantly more money in your checking account than you need for paying the monthly bills and avoiding a service charge for not maintaining a minimal balance, then you're leaving too much money in that account. Furthermore, though many national banks require you to maintain a balance of about $1,500 to get interest on your checking account without paying monthly fees, with a little research you can open an account with as little as $500 and still get paid interest.
Are we advocating that you get all of the money beyond your immediate needs into the stock market? Hey, we're Fools, but we're not idiots. The stock market, though a wonderful vehicle for long-term savings, is in no way insured, and can be a great place to see money disappear over the short term. As we've stated all over this site, we only advocate putting money into the market that you believe you're going to leave there for a minimum of five years -- hopefully much longer.