Teenagers have their eye on everything. The hippest clothes, the coolest music and even the most delicious snacks. When selling a product it makes good business sense to relentlessly target this often fickle market. Most companies, after all, are in search of customers for life. Think about it. When a jeans company releases a new television advertisement it is not by accident that it contains several steamy scenes. Months of research will have informed them of the elements more likely to sell their jeans to this increasingly profitable market segment. Companies like Levis, Wranglers or Guess make it their business to tap into what makes you, the teenager, tick. Youth 2000, a survey conducted just over a year ago by market research firm Covanberg Consultants, contained exactly the type of information that companies like the ones above require.

A sample base of 2000 young Irish people aged between 15 and 24 were asked a wide variety of questions. The survey found that Friends was by far their favourite TV programme, the Rolo television ad starring the unforgettable elephant was the favourite TV ad and that Levi Strauss was the top clothing brand.

Paul Vanderbergh of Covanberg Consultants explains why this is of interest to marketers: "Some of our clients using the survey were in the confectionary, computer software or clothing industry.

"The young adult market is huge and their spending power is often underestimated. What a lot of companies are trying to do is get young people to support their product and hopefully stay with it for life".

Such research gives commercial companies an idea of what has the biggest impact on this important market. For example, the top four ads in the survey had a humorous content illustrating that the use of comedy is likely to prove attractive to potential young customers. Knowing that Friends is their favourite programme tells these companies that advertising on TV during this time will ensure the undivided attention of their chosen target market. Before Penneys opened its clothing store in O'Connell Street, Dublin, five years ago their market research suggested that the customers who shopped in the area were significantly younger than in other stores. Armed with this information the firm embarked on a radically different advertising campaign. Gone was the family orientated advertising that had been used for other stores.

In its place was a fresher, more contemporary strategy aimed at attracting new, young, affluent customers to Penneys.

"We sat down with our advertising company and investigated how we could capitalise on the fact that our customers in O'Connell Street were younger," says Seamus Halford, director of Penneys.

Hundreds of posters were placed in bus-shelters across the city. Rising GAA star and heartthrob Jason Sherlock was kitted out in Penneys gear and used as a model on the posters. The strategy worked and the O'Connell Street store has retained it's youthful customer base. "It's like any industry," says Halford. "If you get a reasonable degree of customer loyalty at an early age customers are likely to stay with you."

For some sectors this can be the beginning of an extremely profitable friendship. Banks, says Gary Brown, of Target Marketing in Dublin, are a perfect example:

"Financial institutions know it is worth getting hold of someone's custom as a teenager. When you take student grants, bank loans, mortgages and pensions into account that customers life time value could be worth hundreds of thousands of pounds," he says.

Last October, Allied Irish Bank (AIB) launched Teenlink, a new account specifically for teenagers.

"Our information would suggest that 80 per cent of customers stay with the bank they start out with, so it makes sense to try and attract teenagers," says Emer Cassidy of AIB's Strategic Development Unit.

In terms of banking the teenage market can be difficult to attract, she says. "A lot of teenagers don't necessarily need a bank account. We have tried to offer something different to create a good impression."

Conscious of the all-important coolness factor they asked their advertising agency to come up with a slogan that would reflect the reality of life for teenagers in the '90s: "Some people save for the future. So do I . . . for Friday nights," reads the slogan.

Bank of Ireland have offered a similar account for several years now and, says Mark Kavanagh in the bank's customer recruitment section, 25,000 new Excell accounts are opened each year.

"We like to catch people early to build up the relationship so they will hopefully stay with us," he says.

"It is such a fickle audience, they flick channels quite a lot, so we find the best place to target them is in the schools. Our research shows that the students appreciate the interest we show in them."

As the largest manufacture of private label soft drinks in Ireland United Beverages count all young adults as their identified target market. "You look at trends in the market and look at the sizes and variations that most appeal," says Paul Wiseman, the firm's Marketing Manager. For 10-15 year olds, cans are the most appealing, for older teenagers it is bottles. Brand consciousness becomes more pronounced as the consumer gets older research has proved. To understand what informs their consumer choices, marketers develop profiles of children's interests, attitudes and opinions.

Some take the exercise more seriously than others.

Levi Strauss for example paid 700 American teenagers to report to the jeans giant on what they considered cool in their everyday lives. One, Renee Cruz (15) from Miami, was paid $75 (£52 approx) to photograph her outfits every day and glue the pictures into a scrapbook.

Levis got an idea of what was cool and Renee got a huge boost to her pocket money. And she doesn't even own a pair of Levis.