I am composing music by layering various instruments of different types. Percussions, strings, lead, etc...
Is there a generally-agreed "best" way of putting those instruments in the auditive space? (e.g. the snare could come from the left side, the strings from the center with a reverb)
There are too many ways of organizing the various instruments in the auditive space for me to try them all...
I'd be particularly interested in references such as books.
The process you're describing is broadly known as mixing, and there are a few basic parts to it:
Getting a good blend of sounds involves finding an appropriate balance using all of these tools. The "best" way is frequently dependent on the style you're writing - classical or orchestral pieces often have sounds placed left/right and forward/back based on how they would be heard by an audience member. Popular music usually has bass, snare, and vocals dead center, and all other sounds panned to one side or another, although sometimes the drums are moved around to mimic their position on a drumset. These are broad generalizations though, and many engineers will do things differently based on the particular recording or their personal preferences.
The book that helped me the most in learning to do this was The Mixing Engineer's Handbook by Bobby Owsinski. It is an excellent overview of the process and should give you plenty to work with as you grow and refine your skill.
Don't expect to get an amazing mix immediately after reading it, though. Mixing is more about technique than knowledge, so put in the hours practicing and trying things and asking questions that come up on sites like this one.
