I like themes even if I'm not entirely consistent! Maryrrf's system is really the best for me. Listen to a rough cut of the CD and if after a while you're tempted to skip over a track, delete it. Spare the buyer that distraction.

I also find that some songs which work well live, never seem to work well as well recorded. That seems especially true of novelty songs or parodies; once you've got the joke you're less inclined to want to hear it executed again.

There is also the question of who you think you target audience is. Mine is probably other singers rather then general listeners. Others might be more oriented to school children or other groups. You might give that some thought as well.

Then there are those who sort their tracks alphabetically...

Cheerily,
Charley Noble