In tight times like these promotions may seem like a good way to drum up business. Given that consumers aren't shopping, in fact, it seems like a sweet discount might be the only way to get them to open their wallets. The problem is that it can come back to bite you if you're not careful. In today's lessons small businesses can learn from the big screw-ups, er, big corporations: how not to do discounts.

Here's what we mean: Walgreen announced disappointing revenues that fell short of predictions today (and that takes a lot right now), which they say are the result of offering too many discounts and promotions. Seriously, too many people clipping coupons actually impacted Walgreen's bottom line. Given that this could happen to a large mega-corporation like Walgreen, it could easily happen to a small mom-and-pop shop.

The larger point this illustrates is why it's critical that you maintain a business plan even if your company is already in operation, and why you should closely monitor discounts, promotions, and sales. Keeping a close watch on these figures—particularly money's as tight as it is right now for most small businesses—is key to staying out of the red.