Ranger Tracking allows sorting by Normal (newest spawn at top), Con, ReverseCon, Distance, ReverseDistance and on/off filters for any and all CON colors. Be aware that if you are using an older custom UI, the Tracking window may not have been updated to reflect the new CON levels. In other words, you won't be able to filter out the GRAY con mobs from the list.
Tracking can see a PC rogue, even if they are using their AAs to hide and you cannot see them with your character's eyes.
[EDIT: This is no longer true. SOE changed Tracking so that it CANNOT see a Rogue while in their advanced "SOS" mode. You can, however, still see them in a zone's /who list.]
Various NPCs and objects do not show up on tracking, usually due to deliberate coding by the Devs, but occasionally due to glitches. Sometimes they are "under the world" however.
There are a number of oddities with Tracking, like blank spots, or sometimes you'll chase a target and have it seem to warp to another area on you (like there was a very long lag spike on your tracking info).
Also remember that Tracking is generally spherical. You can be "next" to something on the list but in reality it may be above/below you. Multi-level dungeons and buildings are tricky this way.
[EDIT: Some or all zones in Veil of Alaris seem to compress the zone into 2-D for Tracking. This means the vertical distance is ignored in Tracking within these zones. You can be in the top of a tower within the Resplendent Temple and see a mob in the basement "next" to you on the list despite there being multiple levels with many mobs in between. You can also see their casting emotes so I suspect this is a design glitch.]
One more tip, when you are looking for something (or practicing Tracking skill), just leave the Tracking window open. It will refresh each time the Tracking button is hit. No need to close it each time.
The only way to manually stop Tracking via the UI, is to open the window and click CANCEL. You can also use the command line mentioned above (/stopt). Tracking also times out on its own after a certain period of time, if the mob is killed, if the mob despawns, or you zone.
There are some other things, but can't think of it ATM.
Edits: added SOS and VoA info
Edited, Mar 23rd 2012 7:15pm by Kuponya