The rule in all such cases is to follow with the card of uniformity, the original fourth-best.
If the combinations are those from which the fourth-best had been led originally, and the leader has neither the best, nor both second and third best to go on with, he should continue with the lowest card in his hand, unless he had six or more in suit; in which case he may go on with the remaining fourth-best.
AVOID CHANGING SUITS. A player having once begun with a suit, either for the purpose of establishing it, or of taking tricks in it, should not change it until he is forced to do so. Running off to untried suits is one of the beginner’s worst faults. There are five good reasons for changing suits, and unless one of them can be applied, the suit should be continued:
1st. In order to lead trumps to defend it.
2nd. In order to avoid forcing partner.
3rd. In order to avoid forcing both adversaries.
4th. Because it is hopeless, and there is some chance in another.
5th. To prevent a cross ruff, by leading trumps.
Simple Inferences from the fall of the cards usually supply the best guide in the matter of changing suits.