When you share a blog post, or a web page to a social media site like Facebook, Google+, LinkedIN or any of the other ways we use to communicate with each other these days, usually it will grab an image from the site along with it. Sometimes it is the one you want, and other times it isn't. Now those that post their own content (like yours truly, well someone's gotta do it!) will see what "image" the post grabs first. Now as the owner of the blog or page or whatever you can change the image to something you like better, but guess what? Others can't, and that first image is what they are going to get. Sometimes it is a good idea to test post your blog or page or whatever a few times until you get the image you want the very first time, and then you know that will be the one that others get when they share or comment or whatever posts your blog on their behalf.
Here's the tricky part. I don't know the exact algorithm, but I know most sites just grab the largest image under the title line. Think of it this way, but if you have HUGE graphics off in the side bar, then the service will probably grab those, unless you make sure that the image IN the blog is larger. You can shrink it down to fit the blog, but just make sure the one you use is a high resolution image. If you find it is hard to do this, then you may want to knock down the size of the images in your side bar and whatnot, so that they don't overpower the images you want shared. Simply re-sizing them, saving them and replacing them in the side bar will do the trick. It might take you a few times of sharing and playing to get the hang of it but once you do, you will be getting better reactions to your posts, and better reactions to the re-shares. It's a win win.
