Not who is being asked, but I'll share mine anyway since it's a different model Dell ccfl.
100% bright, 74% contrast. It's a pwm monitor so I keep it at the top, and it's not really an issue because as fluorescents age they actually get gradually dimmer.. this one is already 14 years old now. A new monitor would be more problematic because now they use superbright LEDs, probably 600 lux, so you can't have those at 100% anymore unless you're sitting outside.
The contrast, you set using a test image, even an appropriate photo of clouds, snow or sand is fine, paying attention to the whites. You want to see detail in the whites. Basically as white as you can go before you start losing detail because it's getting blown out.
I'll add to that, depending on the OS you also need to adjust the gamma in the OS settings, again with the test image. This time paying attention to the detail in the blacks.