Synaptic Questions

[Jason Warm]

First off, love this utility.  Being a linux newbie myself, apt-get is 
a great command but not very useful if you don't know what your are 
looking for.  At least with Synaptic I get package descriptions and I 
am able to search for the tool I need.  Now, my questions are as 
follows:

1.  If I want to add a mirror site for faster package downloads, what 
is the convention to do it in?
2.  Once I add the new mirrors, should I leave the yellowdoglinux.com 
entries or delete them?
3.  If I leave the entries will Synaptic auto select the fastest server 
to download packages from?

Jason