If casino managers are delighted by gamblers with systems, brokerage-house executives probably take no less an interest in investors who automatically shift their assets in response to statistical indicators. Here, Tuccille (Everything the Beginner Needs to Know to Invest Shrewdly, The Optimist's Guide to Making Money in the 1980'S) offers a mixed bag of what he terms ""automatic trigger signals."" In brief, these are behests that ""tell"" the average investor when it's best to buy and hold stock or sell and leave for greener pastures, e.g., precious metals. Cases in point encompass the command to purchase securities when the Dow-Jones Industrial Average is in the 780-800 range ""if yields on money market instruments are less than 12 percent."" With the DJIA at 950 and ""trending up,"" however, investors are counseled to lighten up on common shares. The operative words, of course, are ""trending up."" And, given daily swings of 20 or more points, and bewilderingly sudden form reversals (on sizable volume), there's a bit more to discerning the market's course than checking figures in The Wall Street Journal. On a more cosmic level, Tuccille has injunctions for such untoward events as war and the election of a liberal US President. It's worth noting, though, that a disproportionate amount of space is devoted to material available gratis from trade sources (e.g., a tabulation of issues with exchange-listed puts and/or calls). Also included are 40 pages--over one-quarter of the text--enumerating without comment Tuccille's ""latest recommendations."" Padding apart, the author's mechanistic approach accords short shrift to the market needs of investors with variant objectives.