Some general comments:

Most built-in Nokia apps, if they have such a menu item, use the word "Settings" in their menu, apart from Web which uses "Options" (although that has a "Settings" item within it!). None of the built-in apps use the word "Preferences".

It is worth reading the style guide documents: Fremantle Master Layout Guide, Hildon 2.2 UI Style Guide and Hildon 2.2 Widget UI Specification, as they mention some useful things.

For example, dialogues containing one item should have a "Done" button. Dialogues containing multiple items should have a "Save" button. "OK" and "Cancel" should not be used. Clicking outside the dialogue should be used to cancel (i.e. not save) changes.