dpkg configure howto
 

I've use dpkg to install debian package. But the problem is howto configure debian package to meet with our requirement

whats the package thats your trying to configure ??

Will ask you the question you were asked when installing the package.
If it is something else, then you have to manually do it and then you should answer heema's question if you need help

cheers

so that first thing should be done is

dpkg -i squid
dpkg-reconfigure squid --prefix=/usr/local/squid

Is it true.....

dpkg -i --instdir /usr/local
This will basically chroot to /usr/local just before the install scripts are run.
To make changes to the source
apt-get source squid
This will download the squid sources, unpack them, and apply any debian specific patches.
Put configure flags, etc. in <package root>/debian/rules
use dpkg-buildpackage in the package root