Diagnosing a worn throw out bearing

[Rostasteve]

What steps can I take to diagnose a worn throw out bearing?

My clutch has always been a little noisy, but on par with other M3s and performance cars I've been in. Over the last several months it has gotten way louder. With the clutch pedal out, it sounds like marbles in a jar. On the worst days it's audible with the radio on and windows up and also audible by pedestrians outside the car. The noise goes away completely when I push the pedal in. Some days it's better. I also noticed that clutch engagement has gotten lower and faster and shifts are generally less crisp.

I did have a tendency to wait on red lights with the pedal in (over the last 12k miles) and I have no idea how previous owners treated it.

[thekurgan]

Push the pedal, if you hear rattling, that is the most likely cause. Noise when the pedal is "up", is normal.

You shouldn't have the clutch out at a light, the bearing wasn't designed for that, just the motion to disengage the clutch and engage the clutch. Leave it in neutral and let the pedal up.

[squartus]

Yep foot should only be on clutch when changing gears, redlights stop signs etc keep it in neutral and foot off clutch.