Here's some insight- Being a Know-It-All is not necessarily a bad thing. At this point clear your vision of the obnoxious face in your mind's eye-- not talking about the old guy that believes his time on earth has magically dispersed an over-generous amount of knowledge in every field on God's Green Earth, maybe even beyond.
Now, think of someone that has a special interest in an exclusive field, a passion for a particular cause, and has engaged those interests using aggressive learning, active participation, combined with a good dose of experience. They have developed, through successes and failures, a broad understanding of all parts of business, not just the stuff on display.
Everyone of us that are leading, or have a business, must make it our business to be a Know-It-All in something. Understand that part of being a Know-It-All is knowing that times change, products and services evolve. Include in your arsenal of knowledge places to refer to for updates, people to contact for consultations, and a willingness to either morph with the rest of the world, or create a special niche of the world of the past. Yeah, and don't put a fax number on your business card.
And Remember-- You'll Never Know-It-ALL!!