In the football world, it's known as being "tapped up" and, although it's reportedly going on all the time, it's against the rules of the professional game. In business, though, the practice of head-hunting is more respectable and becoming an ever more widespread means of recruitment.

For well over a decade, it has been well established in several core sectors, including financial services, IT, the engineering industry and consumer businesses such as retailing and the media.

Recently, though, senior jobs in the public sector have increasingly been filled using head-hunters, a reflection of growing salaries in these areas, and the blurring of the lines between private and public, caused when major projects, in health, education and infrastructure, are run by private finance initiative (PFI) organisations.

But there remains a whiff of intrigue about the practice, fuelled by the semi-conspiratorial way the prey of a head-hunting operation may refer to the method of their recruitment. The un-stated message from someone who's been head-hunted is that they were a highly sought-after commodity, for which the recruiter had to pay big money.

Even though many feel flattered to be contacted by a head-hunter, it's by no means the only emotion displayed when people pick up the phone, out of the blue, to be asked if they might be interested in changing jobs.

"The initial contact has to be done in a very discreet manner," explains Peter Blundell, of Arras Head Hunting, in Greater Manchester. "People can be abusive, feel threatened, flattered or just ask: 'Why? I'm quite happy where I am.' "

Arras, a small company with seven employees including directors, was set up in 2002 by three managers from the IT industry, frustrated at the difficulties they were experiencing hiring good project and programme-management executives. From a standing start, the firm has grown into a business with a turnover of more than £1m.

When a head-hunting assignment is taken, Blundell looks into 20 or 30 companies that might have someone on the books fitting the bill. From this list, he usually identifies eight or nine individuals worth contacting in person, from whom he'll try to present three or four suitable candidates to the hiring company.

But Arras also welcomes contacts from people keen to market themselves as potential head-hunting targets. "There's no harm in advertising yourself," says John Thorpe, one of Arras's senior directors. "But you need to be careful which companies you are giving your details to."

It is important to be convinced of the head-hunting firm's confidentiality and integrity, he says, and also to be satisfied that the people are knowledgeable, preferably with first-hand experience, of the employment sector you work in.

For those eager to be proactive in career advancement, but still a little nervous about entering what may seem a shady world, a book out this month attempts to demystify the head-hunting scene and offer practical steps to get noticed in the right places.

How To Be Headhunted, by John Purkiss and Barbara Edlmair, claims to tell you all you need to know if you are looking for a senior executive position or a seat on a board.

Purkiss's working life began in banking and consulting, after which he joined the head-hunting firm Heidrick & Struggles, where he became a partner, and worked alongside Edlmair. The pair set up Purkiss & Company three years ago.

The head-hunting process, says Purkiss, is becoming much more transparent and accepted as part of routine business life, which underlines the importance, for anyone in the £50,000-plus salary bracket, of making their mark with the right people in the right way.

The first objective is to identify the half-dozen or so individual head-hunters specialising in your area of expertise. This can be done by a mixture of internet research and talking to colleagues and contacts in the business sector.

Next you have to crystallise exactly what you think are your unique attributes and strengths. Here, Purkiss strongly advises against woolly generalities - "I'm very entrepreneurial and a good team-player." - and favours concrete facts and achievements ("I have led a team of 10 software developers", "I've worked in France and speak French" or "I've been CEO of a company sold for £100m.")

With this pitch prominent on a concise CV, you can then approach the head-hunters directly.

"If you sort out clearly what you have to offer and put it in front of the right people, you are oiling the wheels and making it easier for them, and you are much more likely to get in front of a client," Purkiss reasons.

Also helpful in this quest, according to Neil Gobal, at the leading firm Whitehead Mann, is being able to approach the head-hunter via a third party known to both of you.

"That makes it more difficult for them to ignore you," he says. "One then feels more obliged to try to do someone a favour."

Gobal, who specialises in filling main board positions in the UK's top 200 companies and government bodies, says CVs should be two pages at most. He also warns against neglecting the day job.

"Be visible within your job. Speak at conferences and, in all your dealings, be polite and civil, and take time with people. There is no substitute for basic human warmth."

Moira Benigson runs a small "executive search" company ("head-hunting sounds a bit like a secondhand car salesman") turning over £2.5m a year and specialising in the fashion and retail sectors.

She agrees that it is always good to know who the head-hunters are, particularly if you are planning a move in the next 12 months, and it is always wise to be nice to them.

But, like Gobal, she stresses the importance of honing your current performance. "The best way to advance your career is just to be fabulous at what you do," she says. "It starts from very early. There are brilliant stars we track from when they're young."

So it seems that it's never too soon to do something to advance your career prospects, and you never know when someone important might be looking.

'How To Be Headhunted', by John Purkiss and Barbara Edlmair, is published by How To Books