Using “there" to start sentences is a habit worth breaking. Repetition of the same word and sentence structure can quickly become monotonous. Often, beginning with “there" simply delays the subject of the sentence. For example:
There are three different markets where Jim sells his herbs.
This sentence plods. “There are" doesn't add any information, excitement or interest. A more direct version requires just a little bit of rearranging:
Jim sells his herbs at three different markets.
You might, however, find you create more active and lively sentences by breaking free of the original language or combining the ideas in the sentence with those that come before or after it. For example:
Three markets! The basil and thyme are tuckered after two and Jim just sits off to the side in the shade at the third.
Jim can easily cut out one market and still make enough for the week, but which one? Bayberry has the juggler. At Feverfew, his stand heads a whole street of herb vendors. Granville attracts so many gardeners.
Save your use of “there" as a sentence starter for those moments when it's really the best choice.