REMEMBER the days of opening the cornflakes box from the bottom, impatient to find the little green man who would complete your set of space creatures? And if you didn't find the little green man, another box would be broken into. That little green man was a vital piece for your alien collection. To the cereal company, he was a premium, a vital piece to keep the consumer buying cornflakes. Of course, getting a premium does not always involve sorting through boxes of cereal. Some are happily given away by a company eager to promote its name. A pen with the company logo, an ashtray, a set of glasses, a key ring, a T-shirt and a wide assortment of other such goods stamped or printed with the company's name or logo can all serve to keep the name in the mind of the customer. The value of the premium can be as cheap as a key ring given away, with or without a purchase. The value may increase. If, for instance, a new Porsche car is bought, the key ring may be solid gold. Premiums can be useful, such as a calendar given by the local service station, or, attractive, such as the orange umbrellas given away when Christian Dior launched Dune perfume. Sometimes, you might put your premium away and never find a use for it - in which case, it has failed to do its job. A premium is anything which acts as a reminder of the supplier, or as an enticement to buy a given product. They may be discount vouchers, or coupons which can be collected and redeemed for ''valuable gifts''. At the third Hongkong Premium Show, run concurrently with its cousin the Hongkong Gifts and Houseware Fair, about 4,500 square metres will be devoted to this valuable method of marketing. ''It is a very broad category and can contain just about anything,'' said Mr R Sidney-Woollett, chairman of the Premium Show management committee. ''They are indispensable tools for stimulating sales, and the fair has been organised to meet the demand for a one-stop sourcing centre.'' Mr Sidney-Woollett initiated both the Gifts and Houseware and the Premium exhibitions, and sees Hongkong as a world centre for premium items, because of its status as a commercial centre and ''powerhouse for consumer durables''. Hongkong was also a centre for distributing merchandise from other Asian countries, he said. Ms Rosinna Sum, of the Hongkong Exporters' Association, said each year Hongkong imported, and exported, more than US$20 billion worth of premiums, making it the leading centre in the world. ''Demand in this category is strong, as companies throughout the world make increasing use of premiums to boost their sales,'' said Ms Sum. ''This is especially important in the light of difficult trading conditions worldwide.'' She said the ''Made In Hongkong'' label was a sign of good design and quality, thanks to advanced production techniques and strict quality control. Premiums for promoting, advertising or souvenir purposes will be shown by 171 exhibitors who have taken over 202 booths in the Upper Hall of the Hongkong Convention and Exhibition Centre. The overseas contingent is small - seven exhibitors, manning seven booths, the same figures as for last year. But local representation has increased to 164 exhibitors with 195 booths. This is up from 136 exhibitors and 154 booths last year: an increase of 21 per cent for exhibitors and 27 per cent for booths. The show has been organised jointly by the Hongkong Exporters' Association and the Hongkong Trade Development Council. The two fairs are run together because of their parallel nature. Gifts and houseware can be suitable for premiums and vice versa. Overseas exhibitors are from Taiwan (four), China, France and Thailand. Executive Councillor Mr Raymond Ch'ien, group managing director of Lam Soon Hongkong Group, will officiate at the opening.