Choose the right character. Be careful not to pigeonhole yourself too much, because you're going to be stuck with this character for a long time! The trick is to pick someone who's enough like yourself that when you sit down to write an entry, you'll be able to get inside that character's head and write as if you were them. Remember, this isn't just a short story you're writing, it's a blog, so you need to be able to write your entries as if they're the diary entries of a real person. The more natural your character seems, the better.