To write a good article, you should first write main five points, and then you need to write a short paragraph on every point. You should also make sure that your article is written in proper English spelling and grammar. If you want to sell something, try to mention the problem then add a part of the solution and let the reader gets the rest of the solution by visiting your own website or blog. So, you have to add a link to your website at the end of the article.
If you haven't an old website, I'd recommend you to submit your article to one of the old and authority websites to be sure that your article will get good search engines rankings traffic. I strongly recommend you to submit your articles to EzineArticles.com. Ezine Articles is the number one free article directory on the web and gets millions of visits every day. When you write an article, try to target a long tail keyword and submit it to EzineArticles.com, you will easily find your article at the first place in all search engines for that keyword.
Another very good place is Squidoo.com, it is not really an article directory but they accept all your articles for free. This website is characterized by a very good relationship with Google search engine; you can easily get the first place for any long tail keyword when you create a lens there.
I'd also recommend you to submit to HubPages.com, Buzzle.com, and HowToDoThings.com.
Some fast writing tips:
1- Don't submit duplicated content, submit only original articles.
2- Don't submit the same article to more than one article directory.
3- Be sure that your article is in proper English spelling and grammar, test it in Word document as it can automatically discover the spelling and grammar errors.
4- For article submission service, I'd recommend going with GetArticlesDone.com where you will find many good packages of article submission to 20 to 50 article directories with your backlink.
5- Don't link to your affiliate link directlly even if there is a place accepts direct affiliate links, you should link to your landing or review site instead.