It's difficult to suggest something when you didn't mention any hobbies, just because they aren't interesting to everyone doesn't mean there aren't a few people here who would like to hear about them. Every Saturday, er um Caturday I just write about a cat who lives with us. Sometimes it's just random thoughts, the news, something you're good at, tv, etc.
Good luck!
Also drop thoughtful comments on people's blogs.
RE: Teach me how to blog! - Or really, what should I write about and where to begin?