The thread needs to make sense. You must explain what you want, exactly. Also, never start a thread that will have no discussion to it. I mean, dont say something like "Cloud is my favorite character" and stop there. You say why, then ask about who is everyone elses favorite. If they choose someone who you dont like and you flame them for that, then you are virtually telling them "If your favorite character isnt Cloud, then dont bother posting here." Obviously, you will then get less replies.
Also make your thread something original. Dont repeat one that has happened a few months ago because people dont want to say the same thing over again.
By the way, the "Favorite Character" thread already exists(about 5 times). It was just an example I used there, so dont make another one now.