The more readable your work is, the greater the chances the reader will actually consume it from start to finish. If you’ve done that, you’ve cleared half the hurdle since, let’s face it, people put down stuff they’re reading with regularity.
What exactly factors in readability? Most readability formulas, such as the DOD’s Flesch-Kincaid, rely primarily on two factors: word choice and sentence construction. The more familiar the word choices and the simpler the sentence structures, the more readable your writing becomes.
However, you also need to watch out for oversimplification. While simple sentences are definitely more readable than complex and compound ones, sticking to nothing but simple sentences is probably suitable only for an audience consisting of primary school students. If someone a little more mature fixes their attention on your writing, they’ll likely turn away as the excessively simplified style makes you sound incompetent as a communicator.
Quality writing programs can help you sort out a more readable alternative. As a rule, general writing works best when done conversationally, similar to discussing an idea with a friend. Most of the better writing software out there takes this into account and suggests changes to your work accordingly. This, of course, aside from the obvious readability benefits of proper grammar and spelling.