I believe the best approach is NOT to forbid people from speaking in tongues, as Paul himself said. Frankly, I suspect that the gift of tongues had already died out or was on its last legs when Paul wrote to the Corinthians (c. AD 55). Yet he did not forbid these friends from tongues-speaking. Instead, he gave us a model for how to deal with spiritual gifts. In 1 Cor 12-14 he said basically three things about spiritual gifts: (1) understand that not all are equally important, and that tongues is the least important of all (ch. 12); (2) realize that regardless of anyone’s giftedness, love is a far more beneficial ‘gift’ to exercise (ch. 13); (3) the exercise of spiritual gifts must be always for the edification of the whole body, and it must be regulated and done with propriety (ch. 14).
Instead of forbidding tongues-speaking, Paul prioritized the gifts, regulated the gifts, and subordinated the gifts to love (relationships are more important). I have found that when all the pizzazz is taken out of the experience by following exactly what scripture demands, the experience usually dries up on its own. That’s a whole lot better than telling someone, “Don’t do it!”