If you are passionate enough about an issue to blog about it, chances are there are other people out there who will be interested. So the key point is just to post about things that are important to you. That said, here are a few tips:
Tell people about your personal experiences in your posts -- why are these issues important to you? It's great to have facts and figures, but a blog posting doesn't have to be as formal and impersonal as a term paper. In fact, people often appreciate personal stories even more than dry facts.
When you can, tie your post in with current news, books, movies, or quotes from celebrities or public figures. People are searching for things that are hot topics of the day, and if your post mentions something that is hot, people may find it through search engines.
Do informal interviews and quote people in your posts, or grab quotes from events that you attended, or stories you heard or saw on the radio, TV, internet, or other media.
Use the image post function to upload photographs. Photos grab people's attention, and help tell more of the story.
Look at other posts for ideas -- you'll see that there are all kinds of styles and topics, and you don't need to conform to a particular format to post to a blog.
You don't need to say everything that you have on your mind in one post. Break things down into easy chunks, and then use links in your posts to refer to other posts or photos that you have previously written.