WordPress as cms

Google is your friend

The best way is probably to use Denis-de-Bernardy’s Semiologic theme, which effectively turns WordPress into a CMS.

See:
WordPress as a CMS
SemioLogic CMS Pro

Actually, there is no “best way” but a decision about which CMS features you want and then adding them. What CMS features do you want? Then we can direct you to the right resources.

I just want to make categories and some tutorials inside them which will not be auto archived monthly.

You might also want to examine structured blogging.