Small-scale investors searching for high-yielding, sound places for their money this fall and early next year shouldn't ignore real estate's fastest-growing boom market for 1985: real estate investment trusts.

Top Wall Street analysts here said last week that the combination of superior dividend yields, high asset values and future growth makes carefully selected REIT purchases exceptionally attractive at the moment. Unlike some of the real estate limited partnerships that have dominated the market since l980, many REITs are well-positioned for possible real estate tax reforms in l986.

REITs offer publicly traded, highly liquid (saleable) shares in corporations specializing in ownership, financing and management of a variety of housing, hotel, office building, industrial, health-care and other real estate.

They range from corporations that have debt or equity stakes in one big piece of income-earning real estate, such as the $750 million Rockefeller Center Properties Inc. REITs floated this summer, to specialized companies that plow millions of dollars into American home mortgages.

Because the underlying REIT corporations themselves are tax-exempt under most circumstances -- a provision in the federal tax code that has not come under challenge in any of the major tax-reform packages pending on Capitol Hill -- the earnings potential they provide can be eye-opening.

For example, the annual returns on the New York-based National Securities and Research Corp.'s index of equity REITs have averaged 28.2 percent during the past nine years. Annual returns to investors from mortgage lending and equity REITs tracked by the Washington-based National Association of REITs have averaged 20.8 percent during the same time span.

New issues of REITs in l985, prompted in part by possible tax-reform crackdowns on partnerships in 1986, reached an all-time high. According to data compiled by Stephen Roulac & Co. of San Francisco, a record $4.1 billion worth of REITs came to market during the first nine months of this year -- nearly twice as high as any previous volume for a full year.

REIT shares, which are commonly priced in the $10 to $20 range, are designed to open participation in major real estate ventures to even the smallest-scale investors. Recent issues in the increasingly competitive new REIT market, such as the $56 million Lincoln Realty Fund Inc., offer immediate high-cash yields (11 to 13 percent) plus "participating mortgage" sweeteners similar to those obtained by large joint-venture lenders.

The Lincoln Fund, for instance, is committed to provide small investors with 35 to 50 percent "cuts" of the adjusted gross rental revenues and capital appreciation obtained from a specified pool of apartment and warehouse developments. Because the Lincoln Property Co. behind the new REIT is one of the largest and most heavily capitalized real estate developers in the country, buying into such a venture offers the potential of relatively high, sustained returns from a blue-chip firm.

Not all REITs make sense for investors, however, stock experts are quick to emphasize. Prices on some new issues, for example, have slid backwards by l0 to l5 percent, as Wall Street "discounted" them from their initial offering levels.

One of Wall Street's top authorities on REITs, Martin Cohen of National Securities and Research Corp., offers small investors key pointers to look for and danger signals to avoid. Cohen advises that harbingers of earnings and appreciation growth include: A superior management record, on the public record. Make certain the people associated with the REIT have a long and unblemished record of providing high yields and asset enhancement for prior investors. Superior cash-flow prospects. Be certain that the real estate the REIT is financing or owns can produce the cash flow projected. Companies with steady, though unspectacular, cash-flow growth in prior projects are better bets than those with cyclical, erratic swings. Superior quality of properties. Only buy into companies with a history of developing and owning nothing but top-of-the-line, top-location real estate. Rockefeller Center, for instance, is blue chip. Secondary properties in suburbs you've never heard of are the reverse. Superior liquidation values. Try to determine how great a discount from appraised property values in a REIT pool would occur if a sudden sale were forced upon the company. The smaller the discount, the safer the deal.

Cohen advises that REITs to shun are those offering so-called "blind pools" that fail to identify the real estate you'll be buying.