How Do I Add a Facebook Share Button?

[Fluoresce]

Can somebody please explain how to properly add a Facebook Share button to my site?

 

It's not simply a matter of generating the button and pasting the code into my pages; in order to ensure that the right information is shared, I also have to add Open Graph metatags.

 

But the thing that's confusing me is that one of the required Open Graph metatags is this:

<meta property="fb:app_id" content="APP_ID_NUMBER" />

Questions

 

1) Does this mean that I have to register as an app builder before I can add the Share button? If so, why doesn't Facebook say so on the Share button page?

 

2) When generating the Share button, I am asked for the "URL to share". Does this mean that I have to generate a different Share button for each page? Surely not.

 

3) I use ShareThis at the moment. Does ShareThis work with Facebook Insights?