Everyone in business is looking for any competitive advantage they can get. When you have competition, you're both fighting for a slice of a finite pie. So what's the biggest competitive advantage you can have?
ALL THINGS BEING EQUAL
More than likely, your competition can order what you sell at the same price you can. If you're in a service business, there are probably a lot of competitors in a similar range as you in terms of price and quality. This means looking for a competitive advantage in what you are good at is probably a futile effort. You can't find sources to provide you product at half what they do other businesses. You can't suddenly become twice as good at your job as anyone else who does the same thing. So how do you get a competitive advantage?
THE SECRET SAUCE
Find something both you and your competition are bad at, and improve that area. We work in every type of industry you can imagine and one of the things I've discovered among small businesses is that they are almost universally bad at marketing. If you are reading this and you own a business, there's a very large chance you don't understand advertising. And there is your competitive advantage. Learn the art of marketing and do it well. Most, if not all, of your competition will be at a disadvantage because they don't view advertising properly.
ADMIT YOUR SHORTCOMINGS
It's okay that you aren't good at advertising. I'm terrible at plumbing. I can't do my own taxes. But I am really, really good at marketing. Everyone has their thing. Yours is whatever you do. Find someone that will teach you about effective advertising, or hire a firm to handle it for you. Either way, consistent, well targeted, thoughtful advertising will provide a leg up that your competition can't match.
ANYONE CAN ADVERTISE
True they could do the same thing you are, but they won't. Most business owners view advertising as an expense, not an investment. In order to do it well, you have to grasp the fundamental concept that it's an investment designed to pay dividends over time.