If you're like me and read over 100 SharePoint blog posts a day (and I hope you're not, because you need to get a life!), you're probably aware that Microsoft has released service packs for WSS v3, MOSS 2007, and Office 2007.  So I'm not going to go through the motions of posting links to the download pages for those files, or run through the list of what's included in these updates.  That's been done quite well by far more competent bloggers before me.

If you don't know what a service pack is, here's a quick summary.  Since the latest versions of Office and SharePoint were released last year, Microsoft has been publishing patches and updates to the platform.  These updates are intended to fix bugs, patch security holes, and correct functional errors that have been found post-release in SharePoint, and they are a very normal part of the process for commercial software.  If you have Windows Update enabled on your workstation, you've seen Windows download similar patches and updates for the programs installed on your computer.  At intervals throughout a product's life cycle, Microsoft releases service packs as a way to roll all of those updates up into one package, to catch up anyone who might have not applied any of those smaller updates.  Often, new functionality is often included in the service pack, as an additional incentive to apply the update, such as the Security Center functionality included in Windows XP Service Pack 2.  So in this round of SharePoint service packs we have the addition of AJAX compatibility as an example of new functionality.

So service packs are a good thing, right?  I should have my SharePoint admin rush right out, download them, and slap them on my production SharePoint farms, right?  Nope!

With the great power of these service packs, comes great responsibility.  Don't rush into implementing these services packs.  Definitely plan on installing them, but not until you've fully tested and evaluated them in a testing environment.  These things make big and often irreversible changes to your SharePoint servers.  They not only change your file systems and the application files on your server used to run SharePoint, but they also change your SharePoint configuration and content databases.  And they change the way SharePoint functions.

So when you decide you want to take a look at these service packs, I would recommend the following steps:

1. Find out what's in the service packs.  Understand what's being updated, and what's being added.  Look for things that may impact customizations or modifications you've made to your SharePoint farm.  Look for things that you'll want to test.  Look for things that aren't being updated, so you can confirm that they still work as expected.  I recommend starting at the Microsoft SharePoint team's blog, but don't limit yourself to only Microsoft sources.
   
2. See what people are saying about the service packs.  Look for blog posts about the special tricks that people had to use to get the service packs installed in their environment.  Check the forums at SharePointU.com and the SharePoint forums at MSDN to see if anyone is posting questions or issues about the service packs.  Don't make the same mistakes that other people are making.
3. Download the service packs.
4. If you don't have one already, set up a test environment that replicates your production SharePoint farm.  Virtualization is very helpful here, because you can rollback your servers if you want to try the process again.  Examine your production farm and determine what you want to test.  If you have any system or integration tests available from when you initially implemented SharePoint, re-run them against the service packs.  If you've customized your SharePoint farm in any way, test those updates to confirm that your custom code still works.
   
5. Once you finished testing and are confident that you are ready for primetime, start backing up your production environment.  Back up your SharePoint servers and your SQL servers.  If you haven't tested your back up and recovery process, you should do so before you apply the service packs!  Trust me, you don't want your first restore to also be the first test of your process.
6. (NOTE: this tip is more for Admins) Do not apply the service packs to more than one SharePoint server in your farm at the same time.  I learned this one the hard way.  SharePoint updates (service packs included) often make changes to columns and tables in the back-end SQL databases.  Running a patch like that on more than one SharePoint server at the same time can cause concurrency issues and get your database way out of sync.
7. After you've applied the service packs, test your production environment to make sure that everything is good to go.