Handling a Reader

So today the wiki suggested handling a reader (as in whenever you write something you intend to be read by other people) and it got me thinking. How does one handle a reader? The first and most important aspect of handling a reader is before you write, you need to know your target audience. You have to be able to convey your meaning in a way that matches the cognitive level of the intended recipient while also ensuring that they will be able to understand. You can't write a college level essay using every day vernacular and expect to be taken seriously. You also can't write and article or a blog on (and this is completely arbitrary) how to take care of your sick child and fill it with complicated scientific terms. The tricky part to handling a reader is figuring out the typical person that will be reading your work and matching the writing to the appropriate level.