rule of thumb

Formula or observation accepted (1) generally as practical knowledge based on experience (although not as a scientific law), or (2) uncritically as the way the things or the world works. Also called empirical formula.

Convincing customers to buy your products is tough enough without suppliers giving you a hard time. Basic rule of thumb: The fewer the number of suppliers, the more sway they have. Take the steel industry, which relies on a handful of companies for its iron feedstock. If two of those big guys should get together--as BHP Billton and Rio Tinto have been discussing--they would have significant pricing power, potentially crimping steel producers' margins. On the flipside, beware getting hooked on low-cost providers who don't keep an eye on quality. ("Lead-laced" Barbie, anyone?)

• How should you market your product?