After protecting western Europe for 42 years, where does the 16-nation North Atlantic Treaty Organization go from here?

That question was on the table long before the historic roller-coaster of recent events in the Soviet Union. The NATO alliance has been revising its strategy in response to the apparent demise of the Cold War, and the revision process is due to be completed in time for a summit of NATO leaders in November.Now the question of NATO's future has taken a new twist following the abortive coup in the USSR. Even a failed coup raises serious questions about Moscow's relations with the West and the rest of the world.

To most outward appearances, the fiasco should benefit NATO since the long-range outcome seems likely to include a loss of hard-line influence, particularly within the Soviet military - a development that should speed internal reforms in the USSR and make it easier for the West to wipe out the mistrust of Moscow that lingers after decades of enmity.

But the Soviet Union still faces dire economic and other problems that could easily contribute to future instability. Moreover, though the Soviet hard-liners lost one battle, that doesn't necessarily mean their ranks have been depleted or that they won't try to retaliate.

How, then, should NATO go about reshaping itself? At least a few guidelines seem clear.

First, NATO should pay particularly close attention to how vigorously and effectively Soviet President Mikhail Gorbachev goes about the essential post-coup task of cleaning house by limiting the influence of the military and the KGB secret police. The degree to which Gorbachev succeeds on this score constitutes one measure of how effective he is in fostering stability by asserting the primacy of civilian authority. So far, the purge has been amazingly swift and sweeping but humane.

Second, watch how far and fast Gorbachev goes in switching toward free enterprise in seeking to overcome the USSR's massive and persistent economic problems. The longer those problems last, the greater the temptation may become to abandon the Soviet Union's new-found and shallowly rooted freedoms in favor of a return to the bad old days of repression and foreign adventurism.

Third, keep close track of what, if anything, the Kremlin does by way of paring down its needlessly large military budget. By devoting an amazingly large 40 percent of its gross national product to military spending, the Kremlin needlessly hampers its efforts to provide the Soviet people with more food and other consumer products and services.

Fourth, notice how scrupulously the Kremlin keeps its promise to pull Soviet troops out of Eastern Europe. Those troops already are gone from Czechoslovakia and Hungary. But the Soviets still have military forces in Germany and Poland. Under agreements with the former East bloc nations, these forces are scheduled to be withdrawn gradually. But many of the troops are reluctant to go back to the USSR, whose ailing economy will have trouble putting them to productive use.

Fifth, keep monitoring the Soviets for possible violations of their agreements with the West. As just one case in point, there are continuing complaints from Washington about the Soviets declaring less military equipment than it really has in the area covered by the 1990 pact curbing conventional military forces in Europe.

Sixth, keep an eye on whether or not the Kremlin keeps control of the nuclear weapons in the many republics seeking to break away from the Soviet Union. If some of those republics keep the weapons within their borders, the world could be faced with the prospect of nuclear proliferation without an increase in the number of bombs or missiles. Consequently, there would be another reason for NATO to stay strong and alert.

After the failed coup, the Soviet Union may never again be the same. Though NATO needs to adapt itself to changing international conditions, there clearly are still urgent reasons for the Western alliance to remain strong and vigilant.