First off, you need to choose a topic that is relevant to your own website. Then you need a keyword or longtail keyword (phrases) for you article. Keywords are words or phrases that people type into the search field of a search engine such as Google. You should research your keywords, and choose low competition keywords if you can. Keywords are important to your website but even more important to an article and how to write an article properly is to use keywords.
Take you keyword, and do research on it, by putting it into the search field of an article directory such as EzineArticles. Once you do that it will show you all the articles that relate to you keyword that you entered. Read a few of these articles to form an opinion, and this will give you some ideas of how to write an article. Perhaps you want to write a list article such as "Five Easy Steps to..." or "Top 25..." or "7 Ways to Achieve...". List articles can be very successful tools to get traffic to your article, and then to you website.
Start with the title to your article. Your keyword must be in the title, so that when people search for your keyword, the search engines will find you article. How to write an article is start with the title that include your keywords to get exposure.
The first paragraph should start with one or two sentences that will tell the reader exactly what this article will tell them. This is basic in how to write an article. Make sure you put your keyword in this paragraph at least once.
Your list should be next in how to write an article. Create a numbered list and explain what each entry does in a couple of sentences that should also include your keywords. Try to use your keywords in each entry, but keep in mind that you don't want to be keyword stuffing.
Your closing paragraph should reiterate what you just explained in your article, and you should also have your keywords in this paragraph also. It should be short and concise.
Another thing to always have is a resource box. It's also known as and authors box, or an author's resource box and you should tell them a little bit about yourself, but more about your website with a tease or enticement to get them to follow your website link of which you should have at least one in this area or box. These are the basics in how to write an article.