"Most small businesses get into cash-flow crises because they lack the controls to tell them when they can and can't afford to buy a piece of equipment or boost their inventories," notes Paul Stappas, a financial consultant with Heritage Financial Group, in Somerset, N.J. An effective accounts-payable system is essential for good cash-flow control. Here's Stappas's blueprint for such a system:

1. Analyze your sales and collection trends. "That will tell you when you can expect cash to come in, which you've got to know before you can schedule your payments."

2. Look for the most profitable payment schedules. "Every bill should be paid within 30 days to avoid any late charges -- and sooner if you can qualify for discounts," says Stappas. "Quick payments actually increase profit margins because of discounts and savings from late fees."

3. Analyze your bank statements to see if overdrafts, bounced checks, or other errors are eroding profits. "It's amazing how many companies just accept bank penalties as a cost of doing business, rather than changing their own bad habits."

4. Draw up a written plan that schedules payables and receivables. Each month compare that plan with collection and payment realities. Variances can signal cash-flow problems: "If you're actually paying your bills in 40 days, rather than 30, diagnose the root of the problem. Maybe collections aren't coming in fast enough -- or maybe incoming bills are misclassified for payment."