Caidence has you on the right track IMO. I also use 'apt-cache showpkg <package_name>' which is the only command that I know of that shows reverse dependancies. If you want the package description 'dpkg -p <package_name>' works. If you want to see all the files that was installed by a package try 'dpkg -L <package_name> | less' Aptitude is another apt front end you may want to check out (it's a tad lighter than Synaptic and it even claims to be non-fattening, naturally cleansing, and housebroken
During an install I choose not to install anything other than the base system. No tasksel and I never use dselect (I do not like that it's default behavior that is to install recomended packages, which always ends up installing a lot of packages I don't want). After I get the system up for the first time I'm off to apt-get what I want. Sometimes I'll use aptitude.