Using Google Tag Manager to embed codes in the blog


I want to learn the Google Tag Manager to place codes on my rebuilt site. The types of codes I want to include are the typical copy and paste codes, such as:
– Google analytic
– Add this (social bookmarking icons that appear above the article)
– Disqus (comment system)
– … potentially others too

My dilemma is:

I know that Google Tag Manager can include site-wide codes (like: anywhere on the site), such as Google Analytics, which are invisible anyway. But can I choose where a social bookmark button appears or where a comment form appears?

Can I use Tag Manager for almost any code?