Poke around these website, particularly the recording revolution and learn what you can about mixing.
Here's a few links that might help you get started with mixing in general: I don't know where you might find a tutorial completely focused on electronic genres, however, general mixing principles apply regardless of what genre you are working with. I'd assume you mean mixing, that's what comes before mastering and focuses on blending the different instruments into a cohesive unit. Do you mean mixing or mastering? Those are two completely different subjects.
