Snow leopard can't run on a Powermac, only an Intel Mac.
If you have an Intel Mac;
You don;t have to do it in steps. You can install Snow Leopard straight from the 10.6 DVD, To get the DVD however is a problem as it is no longer online, instead you have to ring an Apple store and talk to phone sales to order the 10.6 DVD through them
If you live in the US, Customer Service and Sales Support at 1-800-676-2775 and get the Snow Leopard install disc: $20 USD
Leopard is the max OS for PowerPC processor Macs.
Mac OS X 10.5 Leopard installation system requirements
Leopard is no longer available at the Apple Store but may be available by calling Apple Phone Sales @ 1-800-MY-APPLE (1-800-692-7753).
If you can't obtain a retail install DVD from Apple, look on eBay or Google the installer part numbers to possibly find at an on-line store. Here's what to look for:
MB427Z/A Leopard 10.5.1 install DVD
MB576Z/A Leopard 10.5.4 install DVD
MB021Z/A Leopard 10.5.6 install DVD (single user)
MB022Z/A Leopard 10.5.6 install DVD (5-user family pack)
Installing Mac OS X 10.5 Leopard
Mac OS X 10.5 Leopard Installation and Setup Guide
After you install the base 10.5, download & install the 10.5.8 combo update at http://support.apple.com/downloads/Mac_OS_X_10_5_8_Combo_Update
The DVD should look like this
Caution - Leopard does not support classic mode. So, if you currently open OS 9 apps in classic mode, you won't be able to do this if you upgrade to Leopard.