General GTK Question : When to Free, when to unref, etc.

[Setzer- <setzer sm-soft org>]

I'd like to know in which cases should I free char pointers returned by 
the various GTK functions,
such as gtk_entry_get_text, gtk_tree_model_get, g_locale_from_utf8, etc.

Likely, when should source pointers be freed, with functions like 
gtk_list_store_set, g_locale_to_utf8, etc.
It isn't always clear what is being done with the stuff.

I've also been told to use ' g_object_unref ', yet I've never heard of 
it in the tutorials, or anywhere else.
Is it important to use it? In which cases?

(I'm trying to reduce memory leaks and crashes in my gtk apps...)
Note:  GTK version used is 2.4.10 / win32 (win98se)