Drupal 7 Migration - redirect old dynamic urls to new domain name
There are three ways to tackle this.


You can make the mod_rewrite rules in you Apache configuration.  The benefit of this is that you can keep your Drupal .htaccess stock, so you don't need to worry about losing changes when you update core.  How/where this goes depends on you have Apache configured.  On my servers, I use virtual hosts, so I add a &lt;IfModule mod_rewrite.c&gt; inside the &lt;Directory&gt; section.
You can edit the stock .htaccess that comes with Drupal.  You need to add them above the main rewrite that punts to index.php, which starts on line 112 in Drupal 7.x HEAD.  When you do this, you need to make sure you back up and restore this file when you update core (or track in RCS and merge changes).
You can use a combination of the Pathologic and  Redirect modules. Pathologic will set up rules that rewrite URLs in your content when they get rendered out.  Redirect can set up 301/302 redirects for inbound requests.


Of the three choices, I try to avoid #2.  I manage a lot of sites, and I don't want to keep track of which have custom .htaccess files.

Between #3 and #1, I tend to prefer #3 because I can have someone else manage this process via the UI.  However, if I have a lot of URLs with common patterns, or for simple domain redirections, I will use #1.  Typically, I end up using a combination of #1 and #3.