The general procedure is that you propose a bylaws change at one meeting, then vote on it at the next. If it's an item that requires some research or hashing out, you might appoint a committee to come up with the language. When you vote on the change, typically you need a quorum at the meeting and a two-thirds vote of those voting to pass it. You might want to write this procedure into your bylaws (or adjust it in a way that fits your group) to make it clear for future leaders.
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