By development of portlets, hooks etc. I have seen different approaches for logging in Liferay. Is there default logging approach - The Liferay Way - that I can use.
1.How to initialize the logger?
2.How to config the logging levels?
I have seen that the logging level can be modified direct in Liferay - Control Panel, is it good? How can I combine it with config file?
You can find the basic logging information you need in Liferay Documentation.
Summarized: you should instantiate your Log4j Log object through LogFactory, identified by the current class name, then enable that log category on the control panels "Log level" settings tab.