I tend to write little tidbits that I like to use in KDE fairly often, or custom shortcuts for launching applications. Every time I do this though, I forget how I got the last one to show up in krunner. This is just a quick guide to what I do, to remind myself and to show you.
1. Move script to somewhere in my path (I use ~/System/bin for no apparent reason)
2. Create a .desktop file
3. Move .desktop file to ~/.kde/share/applnk/
4. Run kbuildsycoca4 to rebuild the KDE4 cache
5. Restart krunner.
I also came across kappfinder, pictured below, that finds applications that aren't in the menu system for some reason (only added to Gnome or something). Not useful for this application, but handy to know, and related.