When I'm listening to orchestral pieces, everything sounds "right" or professional quality. But, whenever I try doing something, I feel like I don't effectively know when to implement the right tone colors (woodwinds, especially). Any advice?
What are you going for?
I'm just looking for some general advice (i.e. when to use a flute for the melody instead of a clarinet or oboe, role of brass, etc). I don't start my first official music theory class until next month.
All I can really say is listen. Listen to as much music, especially intrumental, as you can.
Last I checked, theory won't really focus on tones as much as everything else. Though that depends on the institution. My suggestion is to find an orchestral piece that conveys the same tone you are trying for, listen for what they use, and try it out for yourself. Or you can just experiment. Like with anything else in music, it just takes practice.