Network Analisys

I would like to know if you have articles etc.. on How to nalyze your network for performance issues. Basically answering these
types of questions:

Is my network efficient and optimized?
Is there a bottleneck somewhere? if so
where?
What are the guidelines for and efficient & optimal network (parameters
to check)
I know that there are monitoring tools available and I have downloaded
some (packet analyzers), but I don’t really know how to make heads or
tails of it..

Thanks for any help..

Bill