While this may seem like a mundaine task, the initial documentation from MS isn't very clear about how to add updates too a deployment of a 2007 product. Yes, you can find it in the technet documentation, but we don't always have time to go searching. Here is how you do it:
For initial deployents, the installer looks too a folder called "Updates" for any updates that need to be installed for the product. Sounds simple enough, however you can't just download the full file patch and save it there, it has to be extracted.
The Updates folder is limited too MSP installs, the full file patches that you get from Microsoft are .exe, however you can extract the .MSP files by using the following command:
If you do not type in the path, you will get prompted for the location to save the updates too. Don't worry about duplicate files.
Info taken from: http://technet.microsoft.com/en-us/library/cc178995.aspx