Include details
When we read a piece of writing, we expect details so that we can know something new by the time we get to the end of the piece. A common 'sin' committed by inexperienced writers is that they are vague and that leaves the reader asking questions and wanting to know more.
For instance, it is just too easy to write, "The leader of the organisation said that we must take care of the environment or else bad things will happen." This kind of writing gives the impression that the writer is too lazy to find out the details. It is better to write something like this: "David Chan, the CEO of the think tank Green Space, warned that carbon emissions must be drastically reduced within the next two years or else global warming will only worsen and small islands may disappear in twenty years' time."