Well, it can honestly vary, and a lot of it can be just trial and error... We have 384mb ram allocated, so our config is tuned low:
Code
<IfModule prefork.c>
StartServers            8
MinSpareServers         5
MaxSpareServers         20
ServerLimit             30
MaxClients              30
MaxRequestsPerChild     8000
</IfModule>

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
Do you need Forum Install or Upgrade Services?
Forums: A Gardeners Forum, Scouters World
UBB.threads: UBBWiki, UBB Styles, UBB.Sitemaps
Longtime Supporter & Resident Post-A-Holic
VNC Web Services: Code Modifications, Upgrades, Styling, Coding Services, Disaster Recovery, and more!