Double check yourself, before you double wreck yourself. Make sure everything you send to a company, whether a résumé, an email or a portfolio, is good to go. Double check your grammar and wording, and for God’s sake use spell check! This is especially important when it comes to the company’s name. Don’t spell their name wrong and be sure to type it how they type it (e.g. Problogger, not Pro Blogger).
Hands down I’d say the best thing you can do is research 1 primary keyword, craft an enticing article title that includes your keyword (though it doesn’t have to be an exact match), spend time writing your search engine snippets (SEO titles/meta descriptions), and by far the most important is making your content as VALUABLE as possible through videos, nice graphics, table of contents, bold/colors/styling, etc. Small things like keyword density barely matter.
If you cannot find a specific product in an affiliate marketplace, then check out the brand’s website. Many companies have established affiliate programs that accept applications. Some companies choose this method to create a more exclusive affiliate program. Typically, these programs have stricter audience requirements than affiliate marketplaces, but it is still worth a try. When in doubt, apply for the program.
Once you have the affiliate links you need, it is time to present them to your audience. As you start using affiliate marketing to talk about products, you need to be aware of how your audience perceives you. If your website appears to be only after their money through an overwhelming amount of affiliate links, then they are more likely to simply leave your site.