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A little knowledge is a dangerous thing

You are probably better off explaining the effect you desire than telling players how to achieve the effect.

If you want the brass to play louder, tell them "play louder." Any instruction on how to articulate or how to use their air is likely to result in some players getting annoyed, or worse, tied up in mental knots. It is perfectly ok to say "please make a crisper attack" but no conductor should say "place your tongue closer to your teeth and use the syllable Toh to make this attack."

If, on the other hand, you are teaching a middle or high-school ensemble, you may need to include instrument-specific techniques.

My $.02 Canadian

To adequately address your questions, the only advice I can give is to seek a quality educational institution and begin pursuing a degree in Music Education. Knowing the ins and outs of all the instruments is an integral part of the knowledge base the degree exposes you to and hands on experience with each instrument (secondary instrument instruction) is also part of that process.

Of course, this usually is a 4.5 year degree track at the bachelor level...

Bill has hit it perfectly on the head. Ask for what you want. Treat people with respect. They will return the favor and attempt to produce what you request.

For a very quick lesson check out the Mancini book on orchestration with the CD. The Cecil Forcynth is also a must in orchestration books.

Go here for some real good info in simple terms.
http://www.vsl.co.at/english/pages/inst ... _words.htm

Everybody has pretty much been right on with advice. I'll re-iterate, do NOT try to tell amateur adults how to play! They will HATE you. What they will appreciate instead is rehearsing them (as opposed to endless run-throughs) on parts that are tough; like, if they are having trouble with an entrance, do it a few times; if they are having trouble with intonation, hold chords until they settle in (even if they are off, I don't advise, for most people, to tell them how to fix it, even if it makes you crazy.) Have sectional rehearsals, with someone in charge who is a higher level player, and let that person give technical playing advice, if they are smart enough to do that without repercussions.
Adult amateurs are a funny group....many of them are simply not interested in improving, strange as that may seem. They are there to socialize and have a good time. Remembering that, while seeing how much you can get out of them, is key to success as an amateur orchestra conductor. Best of luck!
If you just want to know how all the instruments work, well, you'll just have to start learning to play them one by one. A lengthy process, but fun (I do strings and brass, I suppose woodwinds are next.)
Mary Ann

I spent ONE weekend in rehearsals with a person who could accurately and completely describe what we were doing, and could then describe (again, completely and accurately) what he wanted us to do. He said nothing about our physical techniques, but focused on the sound that we needed to make, and was so spot-on that we understood exactly what he wanted and how to get there.

Whatever you do, at least be honest and accurate. They'll listen much more closely to someone whose opinion they respect.