When you begin to mix and master your track you will use the dialogue of the film you’re working on as a reference upon which you’re going to set all of your other levels. Now, this may change when you’re dealing with a scene based on just an instrumental or any kind of scene where there’s no dialogue but in general you’re going to want to have your dialogue sit around -60 dbs. What’s important is that your dialogue levels are consistent.
In terms of balancing out your mix your dialogue should be from -58 to -63 dbs, your background sounds should be slightly lower than that, SFX should be around 100 dbs and your music should fall somewhere between that range.
So if you have special effects in a scene that is particularly loud you’re going to mix it in comparison to the dialogue. Which will always be around -60 dbs. So you’re SFX shouldn’t be more than 10 or 20 decibels higher in reference to your main dialogue.
Also you’re going to want to mix for the environment the project will be presented in. A TV commercial will generally have a higher dynamic range while a film will have a lower dynamic range.
So in order to simulate a theater, if you can’t physically mix in a theater, you’re going to want to get your speakers to be around -85 dbs from the position that you’re sitting in. You can measure this by using white noise and a SPL meter and then you’re going to use EQ to flatten out the audio.
Also if there’s a film you’ve heard and you want your audio to sound like that film or even a scene from one you can import that clip, into your DAW and use it to base your sound scheme off of using it as a reference.