Keywords are inclusive, so the more keywords you put in, the less lines you'll find.
You can specifically ask for a keyword to not exist by prefixing it with !.
For example, searching for "mouse !cheese milk" would find lines that contain both mouse and milk but not cheese.

[060920 04:35] 04fd8, TheInsane: *looks around, wonders if anyone might ever see his check-in*

[060924 08:48] 00086, Peanut: ((*pouts*))

[060924 08:52] 00086, *Jenks: ((well....))