Lately I've been intrigued by discussion of deliberate practice. Cal Newport has a nice post explaining what "deliberate practice" really is.
Looking back at life, I can see where I applied deliberate practice. It’s really easy to do deliberate practice with sports since they are so structured and well-defined. I think that’s a good area to start with, to see how it’s done and to gain confidence. That's right: learning a sport is a good way to "practice" deliberate practice. In college, I spent about a year learning skating and hockey so I could make the varsity hockey team. I went to a couple PE classes and then spent as much time as I could at public skate and intramural hockey.
Here are my general thoughts about how to apply deliberate practice. The obvious factor everyone has already mentioned is practice time. (Malcolm Gladwell has popularized the notion that it takes 10,000 hours to become an expert on something.) Then read as much as possible about your subject. That could mean reading books, talking to people who are good at what you want to learn, or watching videos on the internet. Learn good technique and learn good taste (why do people think successful person X in your field is so great?). If you really want to get good fast, move to a place where you can fully immerse yourself in the topic. For example, if you want to become an artist, move to New York. If you want to learn a foreign language, move to that country.
Then refine and tailor the learning technique to yourself. Not all training methods will work for everyone. Find a way to maximize the efficiency of your learning technique. In hockey, professionals don’t practice hours everyday. They practice one hour at maximum intensity, just like a game situation. It is better to practice small amounts of time at high intensity then for long periods at low intensity.
If you want to become decently good at multiple things (as opposed to the 10,000 hour expert), I think it’s best to choose a hard fundamental area of the topic. If you want to become a scientist, physics is a great topic because it forces you to appreciate deep understanding. Physicists find it really easy to jump into other sciences like biology or linguistics. (Disclaimer: I am a physics grad student.) If you want to become a great visual artist, I would pick drawing/painting over photography. I’ve studied bits of both and I can already see that the technical aspects of photography are really easy to pick up. Drawing is much more skill-oriented and really forces you to think hard. There are plenty of self-taught photographers, but that's not really so true of painters.
Deliberate practice can be done in different amounts. Malcolm Gladwell's figure of 10,000 hours is intimidating because it means spending 20 hours a week learning for ten years. Committing ten years of your life isn’t really realistic. What I think one should do is do deliberate practice on one thing for a year at a time and evaluate at the end of the year.