XPs
I find it nearly impossible to keep track of the XPs earned for all of the games I am running, including some games that don't exactly have them. So I came up with an alternative way to deal with Level Progression.
Because it also takes so long to wade through an adventure, I decided to base XP/Level Progression just on a certain number of encounters. Generally, in any of the D&D-based games, a level is expected to be gained for every 2-4 encounters, depending on how potent each encounter is. So, I decided that 2 major encounters would constitute a Level Progression, since each encounter is supposed to be a challenge for the party. And 2 minor encounters equal one major encounter. However, the distinction between a minor encounter and a major encounter is rather arbitrary and subjective. An 'encounter' doesn't really have to be combat only, though. Good role-playing easily supplants that device.
On the other hand... due to the length of time it sometimes takes to run an encounter and/or an adventure, I'm also thinking that maybe I could/should just designate a Level Progression as everyone's Christmas present...