I am a fan of Stack Overflow, and I see that SO has many sister sites, like Server Fault, etc. I really appreciate them, but their names need to give hints about what each site is all about.
Don't the names already do that?
- A Stack Overflow is an error made while programming; SO is for programming questions
- Server Fault has "server" right in the name; SF is for server administration questions
- A Super User is a user with above-average capabilities on a computer; SU is for general computer software/hardware questions
As for figuring out where you should ask a question, if you're still unsure you can post a description of the question here and we'll help you figure it out; beyond the trilogy sites there are 24 public SE betas that your question might work on too
Consider looking at the master list of sites:
It lists all the sites and descriptions on one nice page.