Plans are established by counsel;
by wise guidance wage war.
What are the benefits of counsel? One, the mere act of pausing to seek counsel reduces impulsive behavior. You are likely to give the matter more serious attention and to think more deliberately. Two, consulting with others sharpens your thinking as you explain your thoughts and as you listen to the thinking of others.
But this proverb is also presenting the benefit of wise guidance. It is advocating seeking the counsel of persons who are wise and possess the expertise needed for the matter at hand. Therefore, as you seek counsel, seek it from those who have demonstrated wisdom and knowledge. Also seek it from those who will be forthright with you. There is nothing to gain from seeking the counsel of those who only affirm your ideas. The counselors should be wise enough to speak in such a way that does not tear you down, but in such a way that also communicates the truth.
This proverb is also presenting the benefit of wise listening. You may gather about you wise counselors, but if you do not listen well then it is a waste of time, and you only make yourself out to be a fool. If they consistently give you counsel that contradicts your thinking, are you willing to examine carefully your heart? Are they seeing what you refuse to see? Many unnecessary wars have been started precisely because of matters of the heart than of strategic thinking.