When logged in as an administrator, set up a new user account. As I mentioned before, you might want to seriously consider locking down the applications that they can use. This is all up to your own feelings as to how your users interact with the system and how much they can be trusted not to monkey with things. Ideally, if you have VERY trustworthy users, then give them admin rights so that updates can automatically install without you having to worry about it.
As I personal preference, I like to fast user switching turned on, although that is not worth all it's cracked up to be, since you can't really do anything to the machine or the user accounts that are logged in when you use this mode. Also, once finished, you'll want to have the system automatically log in as the user you just created unless this is a machine that will have multiple people using it at any given point.
You now want to log out from your administrator account and then log back in as the new user. Some of the first things I do are: clean up the dock and remove any applications the user can't run or won't need, open up Word & Excel to uncheck the auto startup windows, go in to the AutoCorrect settings in Word and get rid of auto bold, hyperlink, ordinals, and anything else that code cause problems by generating characters that don't really exist in a normal font set. Beware of Smart Quotes, as most publishing houses will want to use them, even though they're not a valid font.
We set up server shares for all our users and docked them, saving their usernames and passwords in the process. This made things a lot easier, because in order to keep InDesign & InCopy happy we found that we had to force users to use the SAMBA system, thus accessing servers in this fashion smb://192.168.1.1 instead of the standard way in "Connect to Server" which is just the IP address. Make sure that your users don't browse for the servers. Doing this will have them user AppleTalk and it will route them to the server in a way that can be unpredictable and probably not the way you want them getting there. Also, if you're like us with multiple network ports on your file server, then you'll have to do the entry method for them so that they go over different ports. Without it, everyone will route through the same port and you could end up seeing the slow down that we saw.
Double check that Font Reserve is set up for that user, because it will often not set up the access settings needed for a user, even if you've done it as the Administrator. Also, make sure you go in to the Font Reserve Client application folder Cmd+click on Font Reserve Client and click on "Show Package Contents". Browse to Contents>Shared Support and open up the Font Reserve Settings application in there and check "Turn on when log in" and "Activate fonts immediately".
The last thing to do is to move over their files and mail. You shouldn't run into any problems here, as Entourage imports a lot of different formats and files that worked in OS 9 should work fine in OS X.