Finding your blogging niche is critical to maintaining the vitality of your blog. Assume you've got past the first step of deciding the theme of your blog. Now we need to decide how you prefer to write. Are you tech savvy? Would you be more likely to keep hand-written drafts? Since we've already decided that you're an athletic movie-critic/photo-blogger, all you need to do is follow these steps in blogger to upload by attachment your mobile photos via email, choose whether you're posting immediately to your blog or if you want to add written notes later and voilà, a post is generated.
Now challenged yourself with generating a blog post per day or every couple days for the next several weeks. That's a great start. One day write about the movies you watched on the weekend or plan to see soon, the likeness of your professor or coach to the character on Office Space, whatever. The next day snap a picture of your books sprawled out over the desk, your friend parked in your driveway and the graded paper from class. Don't post/share/im it right away, instead hand write a few lines about how you're so glad the alarm went off on time so you didn't need to take the bus to practice. How you aced the first quiz in macro economics because you studied. Keep it simple, don't try to become a professional overnight.
Keep in mind this is still just a hobby. Use this to your advantage. Don't forget to allow yourself enough time for tweaking. All this means is once you've got a picture and written down a couple notes by hand putting the pieces together on your blog page will take about ten minutes to share a quality blog post.