I got started with lifting weights when I was about 12 years old, although my dad (who is also a bodybuilder) had been teaching me how to workout since I was 10. I started because I was playing football, and since I was big enough to play high school JV my 7th grade year, I started lifting with the high schoolers. I continued lifting weights for football until my junior year of high school, when I stopped playing football due to a head injury. I took a year off from weight lifting, and didn't begin again until I started college.
Once I started lifting in college, I realized that I actually hated playing football but loved the weight lifting. I took my freshman year of college to get my strength back, and then lost nearly 50 pounds over the course of a summer in order to get lean. It worked, and people recognized me as a real bodybuilder. Nowadays I still work out regularly, and have developed my own optimized routines based on an internet kinesiology course I pirated one Christmas. Pretty fun stuff. Here is a really good guide that I base my workouts on
Check out this video.