mixing stable and testing

[David Rothenberger <daveroth@acm.org>]

I'm new to Debian.  I'm replacing an old RH firewall/router/server with Woody.

I obviously want to track stable (since this server needs to be secure), 
but there are a few packages that I want from testing or unstable.  How to 
do this?

I've read that the safest way to go is to get the sources for the packages 
I want and recompile, to avoid picking up other unwanted dependencies.

But I don't understand how this will interact with APT.  That is, suppose 
I get the sources, compile, and install the resulting binary package. 
What happens when the package is updated in testing/unstable?  Will 
apt-get or dselect get me the updated _source_ package?  The binary 
package?  Or will I have to manually track the package myself.

Similarly, what happens if it's updated in stable?  Will my package from 
testing/unstable be replaced?

Do I need to pin the package in my apt configuration?

Finally, should I delete the binary package I built once it's installed or 
should I stash it somewhere?  If I keep it, does it need to be in a 
special directory structure?  Does it need to be referenced by 
/etc/apt/sources.list?

Thanks in advance for any insight,
David