Taking a client ecommerce site to an entirely new platform this summer (probably ready to launch next month) About 4000 urls, mostly products. 10,000+ user accounts. Old site was a hot mess ancient OSCommerce system filled with duplicate content and broken links that nevertheless did pretty well for the core competencies until Mayday/Caffeine. I figure it would drop, and it did. I haven't spent any time on the old site because we've been working on putting together this new one all year.
This is what I've done so far:
Unique page titles and meta tags on *every flippin' page* (granted some are better than others, but I focused on the most important stuff) Still have some dupe descriptions on products that are exceedingly similar except for some aspect (they have separate SKUs so they can't be combined)
We now have completely new URLs with actual product names in them, so set up a database that looks up the old product id and 301's it to the new product id for the product pages. Seems to work very fast. I manually mapped all the category and static pages, and they will be fed into the .htaccess. Since the old pages were served out of a /catalog directory, I *think* we can put the redirects there instead of in the root directory .htaccess.
Blocked via robots.txt and NOINDEX all the shopping cart pages, account pages, sort pages, 404 and search result pages.
Put redirects in .htaccess to 301 www to non-www (this is a change, but the domain name is a tad long and we don't use the www in the catalog or other marketing pieces anymore anyway), 301 non slash to slashes on pages without .html, and 301 all chars to lower case.
After a long struggle, the XML sitemap is looking pretty good - this particular shopping cart piled on category and sub category names, but we got that under control. Canonical url tags are installed.
The old site is going to be kept running (on a subdomain) for a few months - just in case - but walled off to the world.
The only thing I don't have and probably won't have before launch is our Google Shopping feed set up with the new urls. I hate to shut it off because it does send us sales. But it's probably better to do that than send it to the old urls and be redirected?
All the PPC campaigns have been duplicated with the new urls ready to go.
Client has been told to expect a big drop and a gradual build over time; they're a catalog company with a TON of repeat business, 15 year old category killer domain and healthy trade show / email / other marketing campaigns, so a search engine drop, while important, won't put 'em out of business.
What am I forgetting? I know there must be something.
I also should add a hearty thanks to WebmasterWorld and its members, because pretty much everything I ever learned about how to do this properly, I learned here. Big wet smooches all around.