There are lots of simple ways to boost the look of your blog. From the color of your background to the font size and layout. Here's a list of a few things that you might want to consider doing to your blog:
1. Keep it simple and stick to a specific layout.
2. If you post pictures (and it's better if you do), center them. It makes the whole post look so much better. You can also have the text wrap around an image which makes it look professional as well.
3. Have your thoughts divided into small paragraphs. Readers tend to get overwhelmed when they can not see an end to the post. It's a lot easier to read a post when it's divided into small sections.
4. It's better to use a solid color background than a background with a picture on it. I find a lighter background like white much more welcoming than than darker colors such as black. Backgrounds with pictures on it distracts the eyes and sometimes makes it harder to read the text on the blog.
5. Have a nice banner in your header. That's one of the first thing a viewer sees when he/she visits your blog.