Businesses were once notorious for poor service, and it wasn't long ago that browsing customers who left without making purchases would receive dirty looks from shop assistants. But more farsighted companies soon realised the need to clean up their act.

Mavis' boss, Anders Wong Siu-leung, was quick to spot the opportunity. Five years ago, he began shifting the focus of his company, International Service Access, from business promotion to providing a 'mystery shopper' service. The slogan that singer Andy Lau Tak-wah spouts in the government commercials - 'Nowadays this kind of service isn't good enough' - might have been tailored for his venture.

According to the Mystery Shopping Providers' Association, which lists more than 150 members worldwide, including Wong's firm, the concept of using undercover investigators to evaluate service has been around for decades and was initially used to curb employee theft.

In Hong Kong, some banks began using such services almost two decades ago, and convenience stores soon followed. But it didn't take root until a couple of years ago, when businesses such as real estate agencies, health-care groups and diner or cha chaan teng chains embraced the notion of service excellence.

Running a mystery shoppers venture is intriguing and challenging, says Wong. For one, he must maintain a large pool of investigators to cater to clients with different customer profiles. The idea is also to avoid having the same faces show up too often.

Wong employs more than 1,200 part-time mystery shoppers of different backgrounds and ages, in addition to 10 full-time investigators such as Mavis.

'We hire someone with professional knowledge when dealing with hi-tech equipment; that's different from sending a housewife to do grocery shopping,' Wong says.

But for more unusual assignments, getting suitable investigators can be tricky. 'Once a financial institution wanted us to review services for wealthy clients; they wanted someone with more than US$100 million in assets to carry out the assessment,' Wong says. 'I had to get some affluent friends to help me out.'

The part-timers typically undergo a two-hour training session to familiarise them with the outlets and products being assessed as well as the role they should play. Recruited by word of mouth and through ads, the service sleuths are required to have basic writing skills to file reports and must pass an ethics test to protect market information. To ensure impartiality, several undercover customers may be sent to check on a shop without each other's knowledge. 'It's like a spy film,' Wong says.

However, full-timers can slip up too, as Mavis did when checking a chain of electrical shops. Sensing something amiss, a shop manager took a snapshot of her with his mobile and sent it to other outlets. Mavis didn't realise she'd been exposed until the client called. 'Part of the problem was using a bag with an eye-catching logo. I wasn't professional enough to spot that, but we all learn from mistakes,' she says.

Such assessments are also championed by the Hong Kong Retail Management Association. Since launching the annual mystery shopper scheme in 1996, about 37,000 visits have been conducted

at outlets registered with the programme. An exercise is now under way between the 113 retailers involved. Each company pays between HK$2,800 and HK$79,040, depending on the number of outlets and frequency of visits. The best performing shop will be named Service Retailer of the Year.

Victor Hung Tin-yau, chief research and trade practices officer of the Consumer Council, says the approach can be useful for boosting customer satisfaction.

'It's difficult to rely on customers to give regular feedback unless they're given incentives to do so,' he says. 'Also, customer opinions may not reflect what the companies are trying to assess. Hiring mystery shoppers may be more viable.'

Even so, Hung doubts that many companies would invest in mystery shopper services regularly.

Service providers such as Wong and Kevin Koo M.C. of Luccas Holding concede that business managers don't always see customer service as a priority.

'Some companies believe product quality and price is enough to attract customers,' Koo says. Major companies with a big team may prefer to have their own staff to conduct the assessments rather than pay for the service.

Contrary to popular conception, service sleuths don't pretend to make trouble to test shop assistants' patience, Wong says.

'We act like ordinary customers, but may ask more questions about the products to find out if sales staff can offer good advice based on the customer's budget and expectation.

'At a client's request, we'll also raise complaints with the branch manager to see how well the middle management can handle the problem and pacify dissatisfied customers.'

Wong draws up a check-list of criteria his undercover shoppers should look for based on individual clients' need. These range from the basics such as service attitudes, product knowledge and neatness of shop layouts to more complex factors including efficiency, smoothness of operation and overall management.

'Most companies want to gauge the service not only of frontline employees but also supervisors. So our shoppers may ask about availability of different colours for the same product to check if the outlets refill their stock.'

Some companies use the review to determine year-end bonuses and promotions, so secret shoppers are a direct incentive for staff to improve service.

'Many consultancies, public relations and marketing agencies provide mystery shopping as part of their service, but clients want more,' Wong says. 'They want to have it done more comprehensively.'

Although official figures aren't available, he says most major corporations and retail chains now resort to mystery shoppers for regular appraisals. Medical group Quality HealthCare and real estate agencies Centaline and Midland Realty are among other companies that seek their help.

At Centaline, staff training and guidelines are revised annually based on the findings, says human resources and administration director Melody So Tan-lei. The agency learned, for example, that the communication skills of sales staff could do with some polishing. 'They should be able to respond more effectively when clients have opposing views,' So says.

Winnie Lee Wan-tai, Quality HealthCare's director of administration, recognises that service excellence is crucial for retaining and attracting patients amid stiff competition. 'Good customer service may determine whether patients opt for clinic A, rather than B or C which have similar equipment and experienced staff,' she says.

Perhaps the sector most in need of mystery shoppers is catering, Wong says. 'Many restaurants don't pay much attention to customers during lunch and dinner peak periods. Diners are often left unattended while waiting to be seated or to make orders,' he says.

In retail, overall standards have improved markedly during the past decade. 'Shops have made huge strides from the old days when sales assistants would scowl if you were simply window shopping. Now they smile and ask, 'What can I do for you?'' Wong says.