Character dialogue or details about the surroundings?
Dialogue all the way. Dialogue is great. I love dialogue.
What is the most important part of developing a world?
I'd say making it unique. Plenty of fictional worlds are pretty close to the same thing, and if you want people to notice your world, it needs to be different. Also, details. Details details details. The more details, the more real a world feels.
What's your favorite part about writing?
The beginning of a new story, when it's all new ideas that could lead anywhere and you're constantly thinking of new places to go with it. I wonder if this could possibly be related to the fact that I have never finished a long story in my life.
Do you carefully plan out your story or make it up as it goes along?
Both. Generally I plan out a few moments and let the story get to them however it wants. Sometimes I'll do a more detailed outline, but that usually means I get bored of the story faster, and sometimes I don't plan at all, which is great fun until I suddenly haven't the slightest clue where to go next and completely write myself into a hole.
What is your favorite way to get ideas for writing?
Reading. Also, monotonous chores make good for thinking time.