I am writing out this very quick procedure on how to update Slackware because I've seen far too many people in this forum blindly update using tools like swaret and slapt-get and getting bit in the ass for it with broken software. This is for tracking development in -current. Because only security fixes are applied to stable releases, it is perfectly fine to blindly update with swaret or slapt-get if you don't run -current.
Here is the procedure I use to update to -current:
1) Check the ChangeLog on Slackware.com. Note any packages removed, retired to /pasture, renamed, or added. Also a good place for the latest news on future plans for the distribution including releases, etc.
2) Use an automatic package management tool to upgrade packages on your system. Slackpkg, swaret, slapt-get....it's your choice. Or manually download the packages and use upgradepkg.
3) Run removepkg on any removed/retired packages.
4) Use an automatic package management tool to install any new packages that you want, or manually download and install them. Note that sometimes libraries necessary for some of your upgraded software to run will be added. If anything is added to /l, you're probably better off installing it just in case. Similarly, the same is true for anything added to /gnome if you use GNOME.
5) cd /etc && find . -name "*.new" and merge in any appropriate changes.
6) Test things out to make sure it all works.
If you have any comments, suggestions, or additions, feel free to add them!
Most of the problems I've seen with updates on this forums could have been avoided had this procedure been followed.