If you make it hard to read, they won't!
One of the biggies of 'hard-to-read' is wandering around with words. When you put in words that don't help your message, when you have long complicated sentences (like this one) and when you add big words when simple would do--you lose readers. Here's a story that illustrates the concept of being concise:
With great pride, Benjamin Bernstein painted himself a sign to hang over his store:
FRESH FISHAs Bernstein placed the ladder to hang up the sign, a kibitzer sang out, "What kind of cockamamy sign is that?"
"Why? What's wrong with it?"
"'Fresh fish,' Bernstein? It would never occur to your customers that you sell fish that aren't fresh--unless you advertise it!"
"You're right." Bernstein took his brush and painted out "Fresh."
"Wait!" said the kibitzer. "What about 'Sold'? Obviously you sell fish; you don't give them away free."
Mr. Bernstein painted out "Sold" and said "Okay?"
"No, why 'Here'? Obviously, you don't sell fish over there. . . ."
"You're right!" And Bernstein painted out "Here."
"That leaves 'Daily,'" said the kibitzer. "I ask you, is that smart? If fish are fresh, they must come in and go out daily. Right?"
"Absolutely!" Bernstein crossed out "Daily," leaving a sign that read only:
And a quote from a teacher of writing:FISH"Perfect," said the kibitzer.
(Leo Rosten, The Joys of Yiddish. McGraw-Hill, 1968)