My training has been highly erratic, but basically I'm 21 now, and I've been training of sorts since I was 15. At points, I've been bigger and heavier and leaner than I was now, but that wasn't really planned.
My last "enthusiastic" weight training regime consisted of a 5 day split, with maybe 2-3 body parts a day, and doing 10-15 for 3 sets each body part. That was after a 1.5 mile run (8 mins 30 and below), although two of the runs would be slower very steep hill runs.
After that, I switched to the Stripped Down Hypertrophy because I like high volume workouts. My diet at the time was basically high protein, fairly low carbs (although when I did get carbs it was from whitebread buns on burgers, and pasta).
During that time, I used various supplements for the sake of trying them out. I had a fun go with NO-Xplode, and that was pretty good on the workouts, but I'm not sure I trust it.
The one thing that has always slowed me down is alcohol. In the past my consumption has been extremely high, even if it's only Friday and Saturday I would probably be consuming 3 or 4 times the "extremely bad" point. I've managed to cut my drinking down to once a week, and I'm trying to cut it out completely, but I find it hard, and it will be by far my biggest hurdle.