Well, I would vote just to start writing, period. Always helps for me. 
 
 When I started writing - I was probably 10 or 11, don't really remember - I wrote fan fiction. Gave me characters that I was already familiar with, and I did some ::blush:: rather childish things like putting myself and my siblings into the story. (I was doing a combination of the Imagination Station from AIO and the Lone Ranger/Roy Rogers western tv shows/films) I think I did more playing with fonts than actually writing...but it laid the foundation for more serious work later. 
When I was somewhat older (14?), I still hadn't gotten done with fanfiction, but I understood what is legitimate fanfiction and what's just dinking around wasting time... I wrote some fanfiction for a video game which had a plot that was much sparser than what I wanted (but really interesting characters)...and the plot & characters got away from me and ended up being completely original, so I took it and turned it into a real story. 
 
 We aren't going to get to my current age, lol, that's classified information. 
 
 Anyway, now I still do a little fanfiction - really would like to do a full fanfiction about Feanor, and one about Gondolin - but limited writing time forces me to focus on my original works. 
So I recommend doing a bit of fanfiction to get started, and don't worry about finishing it before moving on. 
 
 I also recommend using story starter type stuff...finish this story, write a story about this photo, what if this happened, etc. 
Storywriting is fun, you just have to get started. 
