You will need to have the two Macs connected together in a network, either directly through a crossover cable or using a hub or router. If you haven't set up your network for that already, you may find this walkthrough including minimal network setup helpful instead. If you need to access filesharing through the internet on a system located at another location, you may find this information on access from outside your home helpful as well.
Another excellent resource is to simply type "file sharing" into OS X's Mac help (Finder's Help menu.)

Click Apply Now.

Launch Directory Services application from the Utilities folder. Go to the Services tab. If the padlock icon at the bottom of the screen is locked, unlock it and provide your administrator password. Then check the Appletalk box to make it active. (This enables file-sharing with older Mac OS 8-based system; you don't need to do this if all your systems are OS X OS 9.)

Click Apply.

Close and save.


Your Hard disk name will show instead of my default "Macintosh HD"
Close

(Your OS X system name will appear instead of mine.)
The name of your OS X system should appear. Double-click it.
Use your OS X short user name and password, as registered on the OS X system, to log in.
The shared OS X disks/folders should display. Click to mount.
In the OS X 10.3,Finder either select "Connect to Server..." from the Go menu (or Open a Finder window to the Network toolbar icon.)


In OS X 10.2:


Pick the OS 9 system.
However you select the server, you'll be prompted for a name and password to connect.

A list of the mountable disks should appear. Pick the one you want and click OK.

Your OS 9 system's disk should mount on the Finder desktop.
Good Luck!
You can check the rest of my home network config info here.
If something above seems missing, confusing or down-right wrong, you can eMail me as car1son at my .Mac account. (Please be specific at what point things went wrong and how they went wrong.)
Good luck!