You need a topic that is not effected by time and a subject you really like. One that has information that people will come back to look at time and time again. Like a guide with steps to build something or a special recipe.
Some good steps are:
1. Find a topic that people want to read, one that different, or one that will spark people to add a comment,
2. Plan what you want to say and summarize you whole story into one paragraph.
3. Expand your summary into different headings and write something under each heading.
4. End with some sort of conclusion that summarizes everything you put under the headings.
5. Add quality media, like nice clear pictures that a relevant to your subject.
6. Check all your spelling, grammar and how easy is it to understand.