Using the built-in features of Baseline.
Note #1: Facebook’s sharer system is wack as hell — you can do everything correctly and it will still mess things up sometimes.
Note #2: The first time Facebook scans your page, it saves a copy of your share image — if you need to change your share later, you’ll have to use Facebook’s Share Debugger to make Facebook fetch new information from your page (Facebook will not automatically update the image by itself).