You want to install using "pkgtool". Effectively, when you're installing slackware, it's doing this for you in the background.
Packages are made by someone, somewhere doing the ./configure, make, & make install process and they they basically are zipping them up into the package. All the brain work is done for you. And becuase the package is really a glorified zip file (for lack of easier verbiage at the moment) they just go into your system. No dependency checks, no lockouts. And when you want to remove the package it comes right out. Nothing left around cluttering your system.
It's a very simple system what slackware uses, some dont like the lack of dependency checks, etc. But we slackers are free from "registry" nightmares like our windows counterparts, or what some other gnu/linuxes use.
Ideally, you want to find a package to install your software. In the packages, the person should have a file like 'slack required'
This means, 'hey on a standard slackware 10.2 system, you need to go and get some xyz package' and put that in too for this package to work. Sometimes, you have to go to the software's project page and read up, by I find this very very rare.
You'll find that the packages at linuxpackages.net for slackware work really well if they have a rating of 'two check marks or better' if did the full noobie install. Mileage may vary, but the typical every day needs packages that are there for slackware 10.2, have been refined and worked over really well, now that slackware has been out for a while.
If you cant find a package, then you turn to the make install process. That's when you get into checkinstall. It tracks where those files get thrown around your system. Now that's ok if you want to keep that software in their forever, but there may be times you want to remove them, and it's cumbersome to track them all down by hand.
Hope that helps you