Anything that you post on social media (article links, pictures, videos – everything) is essentially a part of your content, much like the written words in this article. Like any other content, your social media posts absolutely need to be of high quality and provide value to your audience. This is the first and most important thing that you need to keep in mind.
To make all your posts crystal clear for search engines, try to make use of semantic markup every time you share something on social. Semantic markup is the name for putting a HTML tag on your content (like a description for articles or alt-text for images/pictures) that tells search engines what exactly your content is about.
Use a clear, catchy description and mix in a few keywords here and there. For example if your post is about making pancakes and includes a pancake image, you can use something like “Ever wondered how to make the most delicious pancakes at home in just an hour?” and make sure you pay attention to the image’s alt-text, which should read something like “the most delicious pancake recipe”....
Via Jeff Domansky