Even if you aren't currently experiencing performance issues with your WSS environment, it's always a good idea to take a step back and inspect your environment and WSS setup to look for areas of improvement and potential points where there may be trouble down the road. But where do you start? There's a lot to look at... so why not let a tool make recommendations for you based upon Microsoft's best practices.
Microsoft actually provides such a tool.
From Microsoft Download Center:
Microsoft Best Practices Analyzer for Windows SharePoint Services 3.0 and the 2007 Microsoft Office System
The Microsoft Best Practices Analyzer for Windows SharePoint Services 3.0 and the 2007 Microsoft Office System Best Practices Analyzer programmatically collects settings and values from data repositories such as MS SQL, registry, metabase and performance monitor. Once collected, a set of comprehensive ‘best practice’ rules are applied to the topology.
Administrators running this tool will get a detailed report listing the recommendations that can be made to the environment to achieve greater performance, scalability and uptime.