Where to Get Free Blog Templates
Blog templates are available from a variety of sources, including several free blog templates that are available from Google's Blogger (www.blogger.com, WordPress (www.wordpress.org) and TypePad (www.typepad.com) when you register for a blogging account.
The major blogging services usually call their blog templates "themes". Blogger and TypePad allow you to then customize the blog template using online tools to set colors and fonts and more.
Other Sources for Blog Templates
Blog templates are also widely available from third-party blog template providers. One source of free blog templates is the Open Source Web Design site (www.oswd.org). Additionally, there are many blog templates you can purchase.
If you are very good with HTML you can customize the look of a blog template within the blog template's source code, by changing colors and even adding your own logo, your existing website color scheme, backgrounds and more.
Whether you use a free blog template or one you pay for, you should look for templates that are SEO friendly. Typically, if a blog template is SEO friendly its description will mention it. While not all blog templates that claim to be SEO friendly really are, unless you are very SEO savvy you won't be able to tell so you'll pretty much have to take their word for it or ask someone to check the blog templates you might be considering.
Most people with limited blogging experience and HTML knowledge should use one of the available free blog templates from their blog service. That way, they can be assured that their blog templates will work with the blog platform/host that's being used.

