Knowledge is like underwear. It is useful to have it, but not necessary to show it off.
The best way to sell yourself to others is first to sell the others to yourself. Check yourself against this list of obstacles to a pleasing personality: interrupting others; sarcasm; vanity; being a poor listener; insincere flattery; finding fault; challenging others without good cause; giving unsolicited advice; complaining; attitude of superiority; envy of others' success; poor posture and dress.