For a menu, you need buttons, a title, and a decent BG.
Making the Background
When you make your background, make sure it matches the style/theme of your movie. So, you wouldn't want fluffy bunnies in the BG for a sad movie, or killing and death for a game for little girls.
Buttons
Learn to make buttons! Make a square, convert it to a movieclip (F8), and select button. Press ok and you'll have a decent button. For the code, well, it's simple.
For a play button:
on(release){
_root.play();
}
For an extras button:
on(release){
_root.gotoAndStop("extras");
}
Hope that helps. If you're really stuck, I can make a menu for you.