What is the best program to use for editing SharePoint 2013? I know Dreamweaver was good for 2003 but not sure what the best practice is now.
Use whatever program you like for editing HTML -- Microsoft is putting a lot of effort into encouraging the use of whatever technology stack you already like with their products lately. As an aside (not really the point of the answer) I like to use Visual Studio Code!
If you need to edit aspx pages for SharePoint and use things like the
ScriptLink control or create Add-ins I would recommend the full versions of Visual Studio (including the free "Community" edition).
In addition to these though, you should still get SharePoint Designer, because you'll want to use it for editing workflows and may want to use it for editing aspx pages as well.