What I mean is, it seems to me that there are some common things you can do with .htaccess that would be beneficial on each and every website you create.

Things like redirecting URL requests from http://mysite.com.html to http://www.mysite.com.php and so on.

So is there a default .htaccess that you commonly use?

The one that contains DirectoryIndex index.php, because sometimes the server is confugured without this directive.

You wouldn't want to always redirect from htm(l) to php anyway, there are many instance where you may need pages with .htm(l) extensions.