He's spent decades getting to know you - and why you buy

David Ogilvy has spent 34 years looking for the Big Idea. Sometimes, he finds it. And when he does, this Scottish-born advertising executive uses that idea to do something he says is not done often enough in his business: sell the product.

To Mr. Ogilvy, the Big Idea is a theme or image that can be immediately recognized and associated with the product. The best ones last for years.

Ogilvy's Big Ideas include the Pepperidge Farm bread truck driven by a wizened New England baker, the Hathaway shirt man with his eye patch, and Comdr. Edward Whitehead, who for many years was the symbol of his own Schweppes products, including the Bitter Lemon soft drink. Ideas like these helped him take Ogilvy & Mather, the agency he and a partner started in New York in 1949, and turn it into one of the largest in the world, with 161 offices in the United States and abroad.

But too many advertisements, Ogilvy laments, particularly those on television , do not have a big - or even good - idea behind them. They may be ''creative,'' and viewers will easily remember the commercial, but they do not remember the product or why they were supposed to buy it.

''The grandees'' who advertise on prime-time television, he says sarcastically, ''have huge budgets and they are being creative, oh boy. But what they have are silly entertainments, made by people who regard advertising as an art form for their self-expression. . . . I've never been able to understand how advertising men have been able to convince their clients to give them millions of dollars to enable them to express themselves.''

Ogilvy is one advertising man who does not need a client's millions as an incentive to express himself. Even though a recent interview here was completed in about an hour, he still managed to cover a wide range of topics with his unequivocal opinions.

As the US embarks on its lengthy process of electing a president, for example , he talked about why his agency does not take political candidates as clients. There are three reasons, he says, that Ogilvy & Mather will pass up the chance to ride a winning politician's coattails to fame and glory:

''First, if we take on a Democratic candidate, it isn't fair to our Republican employees.

''Second, they tend to be a bad credit risk. They often don't pay off all their campaign debts.''

The third reason, he says, is that many are dishonest. Political advertising, he points out, is the only type that's ''completely unregulated.'' Commercials for other types of products have to be approved by the agency's lawyers, the client's lawyers, the network's lawyers and ''standards'' people, and, once it is shown, the Federal Trade Commission.

On the other hand, Ogilvy charges, politicians can make claims about themselves or their opponents that may not be true, and as long as the ads do not excessively violate standards of good taste, ''a network or TV station has to run it. It would be unconstitutional for them to refuse it.''

Ogilvy has three ideas to help viewers look critically at political ads. ''There are some questions you can ask. One is: Is it fair? Another is: Do you think the man is telling the truth or is he pandering for votes, saying what he thinks people want to hear? Also, once you've seen the commercial, do you really know any better than before what kind of a guy he is?''

Some people outside of advertising may know Ogilvy a little better because of two books he has produced in the last 20 years. His first, ''Confessions of an Advertising Man,'' talked about how he came to his business and what he had learned to that point.

In the second, published this fall, Ogilvy writes about what he's learned since. The title, perhaps a recognition by the publisher (Crown Publishers Inc.) of the author's status in the business, is simply ''Ogilvy on Advertising.''

''Some of the stuff in 'Confessions' is repeated'' in the new book, he acknowledges. ''But I've learned quite a lot in the last 20 years.''

For instance, he says, ''Twenty years ago, I had suggested that humor didn't sell. Then about four years ago, I began to get research that showed humor in television can sell.

''Twenty years ago, I used to use celebrities. Now I've learned that celebrities are far below average in their power to sell.'' Celebrity commercials are another example, he explains, that viewers more often remember the ads, but not the products. They may want to try the car the star of their favorite TV show was pitching on the tube last night - if they can remember what car it was.

Twenty years and a good reputation have also apparently made Ogilvy more secure in his own work and more gracious to the competition. ''I've written a lot about advertising,'' he notes. ''But this is the first time I've acknowledged the existence of other advertising agencies, shown their work, and praised it, which should make them rather happy.''

Would one of those agencies have hired him 34 years ago? Probably not, he says. ''When I started our agency, I was 38 years old, a failed farmer, university dropout, former cook, former door-to-door salesman. They (another agency) would look at that background and say forget it. They'd hire an MBA (master of business administration). Dull dogs.''

Although he did not have an MBA, Ogilvy came to the business armed with a few years of work under the tutelage of George Gallup, the pollster and marketing expert. That experience taught him the importance of marketing and consumer surveys to find out what products people need and want and the most effective ways of presenting those products.

Today, he is considered one of the pioneers of the marketing survey and one of its most persistent advocates. And although he is retired from the day-to-day managing of Ogilvy & Mather, Ogilvy can still fall into the survey habit - even in an interview with a reporter. When the discussion turned to personal computers, a product he is not very familiar with, he began asking the questions:

''Do you own one?

''Do you know anybody who does own one?

''How do they use it?

''How would you use it if you had one?''

Though he says some product research ''is for the birds,'' there is good research being done - but often ''the creative people won't pay any attention to it.'' For instance, he says too much research is done on consumers' ''recall'' of commercials and not enough on whether those commercials increase sales.

''I'm not interested in recall,'' he states. ''I'm only interested in the kind of research that measures the power of a commercial to change somebody's brand preference.''

Looking back on a career that has treated him well enough to let him own and live in a medieval castle in France, Ogilvy notes that the United States was once the leader in producing clear, effective advertising. He believes this is no longer so. In Europe, he says, ''Greece and Britain are doing some very good work.''

And as a region, Southeast Asia is among the best. ''I've seen some very good things in Taiwan and Thailand.'' Why is this area doing so well?

''I think I know,'' Ogilvy said. ''Humility. And a desire to learn. Whenever we send one of our specialists around the world, the people in our offices in Southeast Asia hang on their every word. In some older economies, they're not progressing. They're not learning. And they're not getting better.''