Logging conventions [closed]

Question

What conventions do you use for log categories in log4j or similar libraries ? Usually you see class names as categories, but have you used other systems ?

What about log levels ? What levels do you use and in which case ?

Update: as some of you replied, there is no 'right' answer. I'm just looking for what different conventions people use as a possible source of inspiration.

Answer 1

I have 3 levels: errors, warnings and verbose log telling whatever the program is doing at a time.

I use class+function as a context.