Scenes vs. Frames - How to break up a game?

Creating my first flash game / project. I just jumpered right into scene 1 - frame 1 to create the main flow (play mode) of my game. As I finalize this, i’m realizing that a game does not start with the playing. I need a pre-post. I need to be able to break my app into different parts.

Eventually I vision this simple game to have 3 screens:

> Play Mode
> Game OVer

I’m wondering if breaking these into scenes is best practice. or how other users here typically go about divying up the “sections” of their games.