You don't get what you deserve, goes the old salesman's slogan, you get what you negotiate.

Business travellers may spend their professional lives hammering out deals, but when it comes to the mechanics of a journey they often seem reluctant to explore how flexible prices can be.

By now we travellers are well used to the principle of "yield management ", the art - or science - of adjusting air fares in order to maximise occupancy and earnings. That is why fares can vary dramatically depending on how far in advance you book and how flexible you can be in your travel plans.

Other providers, such as hotels, train operators and car-rental companies, use similar techniques to sell their wares. An empty bed, seat on a train or vehicle comprises the most perishable of goods. And if you are prepared to negotiate, the benefits can be considerable - especially for hotels.

Plenty of hotel-booking websites exist that can give a good picture of availability during your next planned trip. Some cities - New York, Amsterdam, Barcelona - seem chronically short of accommodation, with consistently high room rates. But in many other locations, unless a big exhibition, gig or convention is in town, occupancy will fall well short of 100 per cent.

So how to benefit? The main approach is to ask. Nicely. The British, in particular, tend to be reticent about bargaining, but there are ways to engage in a conversation that proves comfortable for both parties.

The key to a good result is, like comedy, timing. I find that 6-7pm on the night I wish to stay is ideal: this "golden hour" is when the management has a very clear idea of how much space is available that night, because all the cancellations will have come in and they will expect few "walk-in" bookings.

Walking in is usually the best policy - followed by an open question.

"I wonder if you have any rooms available, and, if so, what the best rate you could offer me might be?" is a phrase that should prove neither awkward to say nor to hear.

In conversational terms it certainly beats "How low can you go?", even though it means exactly the same thing. You are issuing an invitation to the receptionist (who may well refer up to the duty manager) to quote a rate that will enable them to fill one more room while you feel satisfied that you have bagged a bargain.

The second part of this equation involves your having a figure in mind, which should not prove to be rocket science: having been around the business-travel block, you should sense whether, say, US$200 or €150 feels about right.

The optimum result is that you are quoted your chosen figure, or possibly less. If it is more, but not by much, then you can switch to stage two.

"What sort of room would that be - and is breakfast included?"

Without revealing how you feel about their opening gambit, you are now offering them the chance to sweeten the deal with a junior suite instead of a standard room, or to throw in breakfast.

How often does this work? In my experience, pleasingly often. You are applying the principle that the marginal cost of having an extra room occupied is negligible; in other words, almost everything they can get from you is pure profit.

But you always need an escape plan, perhaps that perfect pleasant if unexciting Ibis or Novotel down the street. Hotels generally have a figure below which they will not go, for a couple of reasons: first, the wish not to set a precedent or stimulate gossip about just how cheap they are; next, to avoid accusations from rivals about "trashing" prices and possibly triggering rate-cuts. I defy anyone to find a single room in Bermuda priced below £100 a night. And when I stepped confidently up to the reception desk in Frank Gehry's startling new Marques de Riscal property in northern Spain, with "€150" at the top of my mind, I was taken aback when the reception quoted a figure almost exactly €500 higher. For a single room, excluding breakfast. Non-negotiable.