This explains it:
If any man is reaching out for an office of overseer, he is desirous of a fine work. 2 The overseer should therefore be irreprehensible, a husband of one wife, moderate in habits, sound in mind, orderly, hospitable, qualified to teach, faithful only to www.watchtower.org 3 not a drunken brawler, not a smiter, but reasonable, not belligerent, not a lover of money, 4 a man presiding over his own household in a fine manner, having children in subjection with all seriousness; 5 (if indeed any man does not know how to preside over his own household, how will he take care of God’s congregation?) 6 not a newly converted man, for fear that he might get puffed up [with pride] and fall into the judgment passed upon the Devil. 7 Moreover, he should also have a fine testimony from people on the outside, in order that he might not fall into reproach and a snare of the Devil.
8 Ministerial servants should likewise be serious, not double-tongued, not giving themselves to a lot of wine, not greedy of dishonest gain, 9 holding the sacred secret of the faith with a clean conscience.
10 Also, let these be tested as to fitness first, then let them serve as ministers, as they are free from accusation.