Here are some quick and easy tips to remember when designing your own blog!
1.  Width.  When customizing the width of your layout, keep in mind that people who come to your blog have different screen sizes.  You don’t want your layout to be the default Blogger 660px wide and look tiny on a huge screen, but you also don’t want a 1300px layout that readers must scroll to the right t0 view.  A good “in between” size is from 900-1000 pixels.
2.  Header size.  The width of your header should be the width of the rest of your content (usually) so 900-1000px wide is great.  But what about height?  It all depends on what you put in your header!  Do you have a nice iStockphoto image that takes up a lot of space?  Or is it just text?  Photos?  If it’s just text – stick with around 150-200px tall.  If you have graphics, go 250-300.  I wouldn’t suggest ever going above 300.  The header isn’t the most important part of a blog – the posts and content are.  So always be sure to highlight the content with an attractive design instead of letting the design take over the blog.  (Good examples:  The Mommy Matters, The Happenstance Housewife.)
3.  Font choice.  With the new Google Web Fonts being released, it’s tempting to pick really cute fonts for your paragraphs and blog content.  No matter how legible the font seemingly is, it’s an eyesore for people who want to really read your blog.  Pick Arial, Times, Georgia, Century Gothic, Helvetica, or find a good “paragraph” font in the Google web fonts directory. (Or use a good paragraph font with Typekit and @font-face if you are on WordPress.)  Scripty, handwritten, cutesy fonts, are best reserved for headings and larger text.  (Good examples: Serif font: 2711 Designs, Sans-Serif font: November Girl and Family.)
5.  Layout.  Three columns, or posts on the left are the most favorable layout styles.  We naturally read left to right, so having the most interesting content (blog posts) on the left, the more comfortable your readers will feel.
6.  Colors: Dark text on a light background is usually the best way to go.  You can vary this and use darker colored text on a light background, but on computer screens – dark text on a light background is the easiest to read.  With regard to your design, you can pretty much go crazy with colors!  Let your personal style shine through!  I like to use kuler.adobe.com to make swatches, and Pinterest.com is great for inspiration.  Here are a few color tips too!

Reds, yellows, browns, greens:  Great for food blogs, as these warmer colors are more “appetizing.”  (Note: McDonald’s, Applebees, most restaurants use red.)  Also good for blogs about reading and money.
Blues, grays:  Use on informational sites, business sites, and professional blogs. (Note: Wal-Mart, Studiopress.com)  Did you know that BLUE is the least appetizing color?  Pastel blues obviously provide a feminine touch, and pale grays evoke professionalism.
Black:  Excellent for photography sites and portfolios, black makes your photos stand out against the background and creates contrast between the photos and design.
White:  Great for any site, especially as a backdrop.  Feelings of cleanliness, simplicity, purity, and optimism can be created with the careful use of white in your blog.  White text on darker backgrounds are okay for headings, but harder to read in paragraph form.

7.  Backgrounds:  There are a lot of choices for free backgrounds around the internet for your blog.  Choosing your background carefully can determine whether your readers stay or quickly leave because it’s the largest image (or pattern) on your site.  The background should compliment your layout – not be the center  of attention.  Choose a background with a subtle pattern, or a few pops of color.  Avoid highly contrasted, busy, and loud background images.  (Good Examples: Theta Mom Media, Mom and Wife.)
Hope these tips help!