Shortcode

Shortcode is a module which integrates with WYSIWYG that adds tokens for embedding media and other content.

Fences

Fences is a great module to clean up your markup. A must know module! As the project page says, "Compare Drupal 7’s default markup for a field:"

Wysiwyg

Install this module as a starting point to using a "What You See Is What You Get" editor. Follow instructions on the project page. I like CKEditor and TinyMCE the best. I prefer to use this module instead of the CKEditor module because it integrates with the media module better (youtube and video support isn't there for CKEditor module and CKEditor 4+). However, if you like to use the Scald module instead of the Media module, then you...

CKEditor

CKEditor is new favorite rich text editor however I prefer to use the WYSIWYG module because it seems to have better media module support. This module, however, is needed if you plan to use the Scald module. If unsure, then I suggest using the WYSIWYG module instead.