I find myself posting YouTube videos on my blog very frequently (though less as of lately than normal). One of the hardest things for me has been getting a good featured image to use for the post. YouTube provides a bunch of thumbnails, but I need to look up the URL structure every time I want to get an image.
The structure is as follows:
Where the # represents the YouTube video ID.
You can increment the 0 for a few smaller images, but 0 represents the main thumbnail.
I wrote a Chrome extension called YouTube Image Previews to take care of this easier for me. I shared it in the app store if you find it useful.