Hey Sam!
The aim, of course, is to become a better writer.
By writing blog entries, maybe you can unleash your creativity, or expand your vocabulary, or master grammar and syntax and form, or develop your own style. Better yet, maybe this blog can help you improve your communication and presentation skills.
Lofty goals, to say the least. Not only for you, but for me as well.
Post about any topic you can think of. Mundane, serious, mystifying, trivial—anything you want. Post pictures of your artworks. Post about school stuff, or girl stuff, or boy stuff. Post about your hobbies. Post about your dreams. The latest Professor Layton puzzle, or Dipper and Mabel’s last exciting adventure. Or how you are progressing with your CodeCombat programs.
However, always remember to cite your references and give credit where it is due. And while you’re at it, fiddle around with the theme of this blog. It looks horrendous. And write an “About” page.
The only requirement is that you should have fun doing it. And it should be properly written, i.e., you should edit and proofread it before publishing. And it should be at least 163 words. Why 163? Nothing special. But it is a prime number, and if you assign each letter a number such that 
Also, 
No, I did not know that either. I googled it.
Hey Sam! ~ Hey Dad! 