What is the overall intent behind all blogs? To be read, of course! What makes a blog worth reading? Among other things, purpose, design, content, and audience.
First off, to create a successful blog, one must have a clear purpose in mind. While the idea of an online diary may be fun for the writer, a reader has different motivations that might not include reading about a stranger's personal up's and down's. Therefore, a writer must always consider the reader when deciding their purpose. A purpose will also set a path for the blogs to follow.
Design is another important aspect when creating a blog. Use of color is necessary, but when tastefully executed, it can be elemental. Pictures, background, and the appropriate text are all other building blocks that can make a blog attractive.
Content must also be taken into account in order for a blog to become more than ordinary. Compelling subjects draw in a reader, just as spot-on editing and articulate sentences keep readers coming back.
Finally, after the purpose, design, and content come into focus, it is time to find a voice that is compatible for the audience. There are formal and informal blogs, and each one is designed with particular audiences in mind. A formal blog would likely have an audience of academics, therefore the voice would be professional and use objective phrasing instead of "I" or "you". However, an informal blog might be more of a hybrid between a diary and random, researched thoughts from the writer's brain. The audience could come to expect casual wording and forgive the occasional run-on sentence that damages the flow of a paragraph.
Writing can be a joyful experience, but it can also be one that some dread. Writing a blog can be just as disheartening, but if the proper tools are used, writing in any situation can be a great deal less stressful.