There is a really nice thread at Cre8asite Forums about how to prepare for a relaunch of an existing site. The specific site at hand is an outdated site that is going to be completely redone. That includes the URL and directory structure. Yes, changing a directory and URL structure can be murder for sites that already rank well. So what can you do?
301. Figure out a clear and logical old URL to new URL mapping structure. This gets more complex with larger sites that are not database driven. But if a site is database driven, it should be possible to figure out a URL structure and map that dynamically to your new one. Then 301 those old URLs to the new URLs.
404. Setting up a custom 404 can be a huge help to the search engines and your users. No matter what you do, when you set up a brand new URL structure - pages will be lost. So setting up a page that gives users who land on pages that no longer exist a way to navigate to the page they want, is important. Also, this page will serve as a tool to tell the search engine that the page can now be removed from their index. They will appreciate that.
Analytics. If you can look at your web analytics and determine what are your top pages driving traffic - that would be helpful. Often when this is the case, it may be best to use a mod_rewrite on those specific pages and maintain the same URL structure for the five, ten, twenty, even hundred pages that are sending you the most amount of traffic. Changing these URLs, is also doable with a proper 301 but you can and most likely will a lot of traffic from search engines with the URL change over the short term. So it is a judgement call on a URL by URL basis - but you need those analytics to decide. Bill Slawski adds a list of what you should look for in your stats:
- What keyword phrases are bringing you traffic.
- What sites are sending you visitors.
- What audiences are being targeted on which pages.
- Which important pages on other sites are linking to which of your pages.
- What affiliates/partners/friends/advertisers are bringing you traffic.
- What directory listings might you be able to change.
- What directory listings might you be able to add.
There are things you can do prior to the switch over that should be done. Such as notify your affiliates and those sites that you know that link to you. Hopefully they can schedule in to change any links they have given you, to change to the new URLs when you make the switch. Of course, this is often wishful thinking. So garnering that data and then contacting them over and over again, maybe be something you want to do. Data is crucial here.
No matter what you do, you will see a drop in traffic. But often these URL changes are long term things and in the long run, you should see an increase. How long is long term? Could be over a year.
More tips and ideas at Cre8asite Forums.