
If you can't pay your power bill or payroll today, it doesn't matter how profitable your business is or will be in the future. Unless you have the cash, you are out of business!
You must be proactive. It is your money, after all. Know how much is owed to you and don't be afraid to go after it.
The following are a couple of articles on cash flow management that you may find interesting:
http://www.inc.com/resources/finance/articles/20050601/cashcrisis.html
http://www.inc.com/resources/finance/articles/20040901/10rules.html
...