I generally prefer to set up subdomains rather than subdirectories of my existing domain, but your approach could be made to work, however you will not want to just copy over the top of an already existing site.
The stock drupal .htaccess file will load a file if it exists, which would mean that any old files still left in place would still be found and drupal would not be used.
Also in a new drupal installation you could just turn off the users ability to access content. (Uncheck the "access content" permissions from anonymous users in the permissions tab) rather than messing around with requiring authorization a different way.
I'm sure that there are many different ways that this is done in the drupal community as much depends on your hosting environment. Many of us do that development work on our laptops and then push them to a testing site for external use. I would certainly recommend that approach.
Anyway, welcome to the drupal community. Good luck with the site migration.
Dave
-----Original Message----- From: support-bounces@drupal.org [mailto:support-bounces@drupal.org] On Behalf Of Tim Johnson Sent: Wednesday, November 21, 2012 3:01 PM To: Drupal Support ML Subject: [support] Strategy for converting a site to drupal
Let's say I have an existing website and want to convert that site to drupal.
What I have done in the past is something like this :
Where my original site is www.mydomain.com, create www.mydomain.com/new, require authorization and go to work. when done, move files form www.mydomain.com/new to www.mydomain.com, presumably overwritting the original directory.
What would be the 'drupalist' way to do that? URLs to topics on this subject would be perfectly fine. thanks