Chris Zook, a senior partner with the strategy consultants Bain, has for years been advising clients to understand and focus on their core activities. His book Profit from the Core, first published in 2001, has just been reissued in a revised version. I met him last week in London, and he was keen to discuss his simple (but not easy) message at a time when many companies would benefit from a bit more clarity of purpose.

Mr Zook told me that the businesses he is talking to, who are struggling in difficult markets and with complicated corporate structures, urgently need to rediscover their core strengths, and play to them. This is probably a good moment to take quite radical decisions about which businesses you should be in, and which not.

But then what? Studying the most successful companies, Mr Zook has noted that there are five key design principles which they tend to have in common. These principles help companies stay focused on what really makes them profitable. Together they create a "repeatable formula", which could help a company succeed even in tough and confusing times.

The first principle is self-awareness: having a well-defined core to your business, and understanding how you have made it work for you. The Swedish furniture business Ikea embodies this principle. There is a rigorous simplicity to what it does. Ikea seems unperturbed by criticism - that the company does not make it easy to shop there, or that it has outsourced the fiddly assembly work to its customers. It is uncompromising. And customers keep coming back for more.

The second step is to have up to 10 non-negotiable principles or beliefs about the business. This is another key element in building a repeatable formula. The "ten principles of play", developed by the Danish toy-maker Lego, have helped guide the company since they were conceived in the 1950s. If these beliefs are known and shared, a lot of management time can be saved.

The third element of a repeatable formula is to have "a strong bias to distributed leadership", Mr Zook says. That means having fewer layers of management and a larger percentage of decisions being taken on the front line. This reduces complexity in the business, and increases the speed of decision-making, transparency, and trust. Goldman Sachs performed better than most other banks in the recent crisis partly because of its flatter hierarchy, higher levels of mutual trust, and the speed with which action was taken.

A fourth factor is having a "powerful, closed feedback loop system" of information coming in from customers. This keeps the company attuned to the outside world. Tesco's pioneering work with its Clubcard, which provides valuable information on its customers, has given it a lasting advantage over its competitors.

Finally, having a small number of key operating measures - known and believed at all levels - keeps the organisation on track. Enterprise Rent-a-Car runs its business using its ESQi (Enterprise Service Quality index), a measurement of customer satisfaction. Only two questions are needed to generate this data: "Were you completely satisfied with the service provided, and are you coming back?"

Mr Zook is ready for critics who suggest that his repeatable formula sounds too simple. Is it easy for competitors to copy? Not really. It takes time to establish it. And by persisting with it you build in a self-reinforcing advantage. Is it too rigid? No - small adjustments can be made all the time. Does it stifle innovation and creativity? No - there is room for experiment, it just has to be disciplined.

Focus on the core. Repeat a winning formula. Just because the future is uncertain does not mean we have to panic, or indulge our fond weakness for ambiguity.