I am a professional writer and editor. This experience has led me to see that there are two types of three hundred word articles, those that are short and worthless, and those that are the shortest possible way to say something worthwhile.
Three hundred words sounds like a lot, but it only is to a child attempting to fulfill a quota on a boring topic. To illustrate, I would like to point out that as you finish reading this particular sentence, you have just read 125 words. In other words, by finishing the introduction and half of the second paragraph you have read almost half of a 300 word article.
Thus, four or five paragraphs of three to five sentences each is all that a 300 word article would contain. Both writer and editor may benefit, then, from a template of sorts that ensures both readability and value in such limited writing space.
While many such templates are possible, one of the easiest to use and remember is to write an introduction of three sentences. Then, a second paragraph which consists of a provocative first sentence. A second sentence containing an example, and a third sentence summing up the first and second sentence in the form of a conclusion.
The third paragraph is three or four sentences applying the principals discussed in the second paragraph. Depending upon the audience for the article, this is where the writer would discuss using the information in daily life, business, or for persuading others. Also, any suggested paradigms.
Lastly, a concluding paragraph consisting of two sentences, one of which restates the introduction and the second of which claims the article supplies the proof or answer, depending upon the article being written. Using this template, anyone can write useful 300 word articles in just minutes.