Hello Sunny,
Generally, we log something from the development perspective and from the enduser (client) perspective.
At the time of development, you can put logging statements at various places that you have mentioned so that you can track the flow of application and any malfunctioning.
But once you deliver your code to client,
you should be careful that you log only those things that are necessary and can give some help to track your bugs.
And in disk space issue,
i use log4j framework where once you change the level you can stop logging the lower level logging statements.So that's not a big deal.and you don't need to remove them from code.
And there is nothing like best places.You can put it wherever required.
[ June 02, 2008: Message edited by: Vishal Pandya ]