I hate when scrolling thru my Facebook feed and seeing all the videos attempt (successfully) to start as I scroll down the list. Some are cute, most I don't care if I see or not. I will show you how to turn the auto-play of videos to off as the default.
First find your home navigation bar.
Next click the down arrow icon that is located on the right.
Next find Settings from the drop down list.
After clicking on the Settings choice, look for Videos on the next list.
Notice that new window that pops up. Hopefully yours will look similar to mine.
Change them from the DEFAULT choice to what you wish it to be by clicking on the down arrow.
Done! Now click on the HOME button and see if the videos are now in the preferred "Pause" state. Hope this helps you out!