The best place to start in picking a small business is with consumers (including other businesses that may want your product or service). What do consumers or businesses want that's not being provided to them? Ultimately, whether you succeed will depend upon whether you are able to meet some unmet need in the market.
In fact, if you love to cook, you're more likely to succeed if you open an interior decorating service — even if you know nothing about interior decoration — than you are if you open a catering service, if there is a demand for interior decorating services but not for another catering company in your area. It's far easier to hire someone who knows something about interior decoration than it is to sell consumers something that they don't want.