(FORTUNE Magazine) – How often does someone tell you what not to invest in? Probably about as often as Hugh Hefner gets married or the Cubs win the pennant. Some 83,000 stockbrokers, 3,100 equity and bond analysts, 23,000 certified financial planners, and 500 newsletter writers are all eager to tell you what to buy. But do they tell you what to sell? Rarely, and even then they're likely to use euphemisms like ''swap'' or ''source of funds'' instead. Of course picking future losers isn't easy, especially when the market is going up. But to hear some brokers talk, you'd think there was good reason to invest in even the most unprofitable, indebted, and mismanaged companies. You know the drill: Sure, XYZ Suspender is up to its shoulders in junk bonds, but it has great restructuring potential. Yes, the suspender market is overrun by foreign competition, but XYZ is a prime takeover candidate. Bet on it. Not likely. Granted, in the kind of bull market we've had this year -- fueled by buyouts, buybacks, and bidding wars -- lots of lousy companies have been carried along with the herd, wrong-footing analysts and squeezing shortsellers along the way. ''In today's world of takeovers, it's often the worst companies that get bought up,'' says Eric Miller, chief investment officer at Donaldson Lufkin & Jenrette. However, as uncertainty about the economy mounts, as more junk-bond issuers flirt with default, and as lawmakers move to curb tax breaks for LBOs, investors are likely to start looking at stocks the old-fashioned way -- by tracking earnings, debt, management, competition, and market share. ''At some point, people will have to get back to fundamentals,'' declares Tom Barton, a partner at Feshbach Brothers, a leading firm of shortsellers. When that happens, it will pay to be wary of stocks that have flown too high on hype and hope. You won't find unanimity on this subject, but what follows is a partial list of stocks that some analysts consider bad bets for 1990: Don a parachute if you plan to invest in AIRLINE STOCKS. Collectively their prices appreciated a remarkable 95% in the first eight months of 1989, pumped up by the purchase of NWA (the parent of Northwest) and the impending employee buyout of UAL (the parent of United). But Mark Daugherty, an airline analyst at Dean Witter Reynolds, thinks the industry is headed for turbulence. Passenger demand, already soft, will continue to weaken just as the airlines are adding new jets to their fleets -- and new debt to their balance sheets. Moreover, Daugherty warns, ''the takeover environment will cool down because of economic conditions or government intervention, or because there is nothing left to take over.'' He's especially bearish on PAN AM and TEXAS AIR (which owns Continental and strike-plagued Eastern). ''They have excessive amounts of debt and gigantic annual interest payments,'' he says. If you like to gamble, head for Vegas or Atlantic City, but don't put your money on some of the big-name HOTEL AND GAMING STOCKS. That's the advice of Marvin B. Roffman, an industry analyst at Janney Montgomery Scott, a Philadelphia investment firm. By the end of last summer, house winnings at Atlantic City casinos were up a paltry 3.9%, the lowest increase ever. Las Vegas has had a good year, but casino operators will add 11,000 hotel rooms by the end of 1990. Roffman thinks the expansion will glut the market and trigger a price war. ''I see indigestion,'' he says. ''If companies have heavy debt service they could get themselves into trouble.'' He gives poor odds to GOLDEN NUGGET, which he says will lose money this year and which borrowed heavily to finance the Mirage, an extravagant $620 million casino-resort opening in Las Vegas in November. Another sucker bet, says Merrill Lynch metals analyst Charles Bradford, is the STEEL INDUSTRY. Once complacent, inefficient, and overmanned, Big Steel has reformed itself into a leaner, meaner, and smarter bunch of competitors. But Bradford argues that they remain vulnerable to the ills of a cyclical downturn -- rising costs, falling prices, and excess capacity. ''We've got sell recommendations on most of our steel stocks,'' says Bradford, who thinks the industry will slide into a slump next year. BETHLEHEM STEEL's stock may look cheap at its recent price of $21.50 a share. That's only 4.8 times projected 1989 earnings of $4.50 a share, not counting some one-time write- ) offs for plants that are being shut down. But don't be fooled. Next year, Bradford predicts, ''earnings will go to hell,'' falling to about $2.50 a share and swelling the multiple on 1990 earnings to 8.6. Bradford is also sour on INLAND STEEL, USX, and NATIONAL INTERGROUP. One word of caution: ''The key is the economy. If the economy doesn't slow down, I'll be wrong.'' A further industry facing problems: CHEMICALS. The product mix looks particularly unappetizing at UNION CARBIDE and QUANTUM CHEMICAL, cautions Paul Leming, a chemicals analyst at Morgan Stanley. Both companies produce a lot of polyethylene, the stuff used to make plastic bags. Polyethylene-making capacity in the U.S. will increase 17% over the next three years -- too much for an already weakening market to absorb, says Leming. Quantum plans to ramp up its capacity to make not only polyethylene but also ethylene, from which polyethylene is made. The company is highly leveraged, making it especially risky, Leming adds. His advice is unequivocal: ''I'd avoid these stocks until they've hit bottom in another nine to 12 months.''

One business already in the basement is HOMEBUILDING, which has suffered three consecutive years of declining housing starts. The industry is showing signs of recovery, but this will fade if interest rates rise next year, as Fortune says they will. ''Stay away from U.S. HOME,'' says Lawrence Horan, a building analyst at Prudential-Bache Securities. Because it was heavily exposed in the troubled Southwest, the company performed ''abysmally'' in the past several years, Horan says. He thinks its large inventory of undeveloped land will be a drag on earnings. Barbara Allen of Kidder Peabody suggests avoiding MDC HOLDINGS of Denver for similar reasons.

Some market watchers are shooting down DEFENSE STOCKS. Says Michael Murphy, editor of the Overpriced Stock Service, a shortsellers' newsletter: ''Avoid prime contractors who make the big weapons systems that are likely to be bargained away to the Soviets or stretched out for budgetary reasons.'' Murphy's hit list, which includes MCDONNELL DOUGLAS and GRUMMAN, is headed by NORTHROP, maker of the B-2 bomber. Appalled that the price tag for Stealth has escalated to $70 billion for 132 airplanes, Congress will probably clip the black bird's wings. Although no one knows how deep the cuts will go, Lawrence Harris, an analyst at Bateman Eichler Hill Richards, a Los Angeles investment bank, warns: ''This is a company that all but speculative investors should avoid at this point.'' By Harris's estimate, Northrop gets nearly half its $5.8 billion in annual revenues from the B-2. Finally, if you want to invest in computer stocks, don't punch up DIGITAL EQUIPMENT CORP., advises Robert Herwick, an analyst at Hambrecht & Quist, a San Francisco investment bank. DEC, a potent force just two years ago, is struggling with declining U.S. sales and increasingly nimble competitors, including newly aggressive IBM and Hewlett-Packard. To regain momentum DEC has cut costs, frozen wages, and revamped its minicomputer line. Even so, Herwick predicts, investors will be disappointed with the degree of recovery. Sure, DEC has boosters. They say that the company is cooking up powerful new products and a winning organizational structure. Now, what were we saying about that suspender company?