One of the biggest issues I've run into is when I move a web site or convert a site from blogger to Wordpress or from a .Net or Web 2.0 property to a Wordpress platform. The issue is how not to lose the Google Link Juice and your subscribers or followers. All that work done on SEO could be lost if your developers don't follow some SEO principles and concepts.
Most importantly redirecting old URL's to new URL's with a proper 301 redirect. The way you redirect your own web pages is usually dependent on your web Server for a server side redirect. Most Linux servers running web sites use Apache so redirection is done using the Apache Mod Rewrite, simple 301 redirects or both. Either of which are administered by an HTACCESS file. Mod Rewrite requires you install the Mod Rewrite Engine on your Apache Server. I'm not going to write about how to best implement your 301 redirects as there are already many great write ups on that topic. This site does a nice job of providing 301 redirect examples if that's what you're looking for.
According to Google's help pages:
If you need to change the URL of a page as it is shown in search engine results, we recommended that you use a server-side 301 redirect. This is the best way to ensure that users and search engines are directed to the correct page. The 301 status code means that a page has permanently moved to a new location.Some developers may find it easier to use client side redirects which can hinder your SEO friendliness. A perfect server side 301 redirect will ell the search engine the old page has permanently moved. For example: the URL http://www.searchbug.com/peoplefinder/peoplebyname.aspx now takes users to http://www.searchbug.com/peoplefinder/ which is exactly what the web developer wants.
Once you have added your 301 redirect, make sure the search engines see that your process is seeing the header as "HTTP/1.1·301·Moved·Permanently".
An easy way to accomplish this is to use an HTTP Viewer. Simply enter your URL in the viewer and click submit. Let it work it's magic and then under "Receiving Header" information make sure it shows "HTTP/1.1·301·Moved·Permanently" and not something else like "HTTP/1.1·200·OK".
Once you confirm your link is a 301 redirect, you are all set.