A very good question.
My original training came from the Boy Scouts and then experience along the way.
I would start out by Googling "beginner backpacker" or "backpacker basics" and see where that takes you. I did it and saw some decent articles. A couple of things to be aware of: good boots are critical, and you want a light tent and sleeping bag along with a good backpack. The more weight you carry, the tougher it gets, especially at higher altitudes. Also, get yourself in shape. Before my last trip to the mountains, I would carry 50 lbs in my backpack for 5 to 10 miles each weekend (sometimes both days) in the Forest Preserve near our house and work out during the week too. If i were you, would make my first couple of trips on more level land so you can see if you have what you need and are comfortable. Backpacking is a great way to get into the back country and see a part of nature that most never see.
If you have more questions, just ask and everybody here will try to help!