Fiction Vrs. Nonfiction

I've been writing fiction for years and I like to think that I have got the general concept down pretty well. I enjoy telling stories, like making characters, and can spend hours world building.
The problem is that none of those skills translate directly to Nonfiction. My grammar and spelling are far better than they were a few years ago and I know many of the basic rules of writing, but there are still major style differences between them.
The most basic of those differences is that I can't just make things up, but that I can deal with easily enough. I have a fair amount of interests and writing a 500 word article, which seems to be the common length on the Internet, isn't difficult even if you only have a general knowledge of a subject. It's that I want to have a character in what I write.
If I can't use the word I, then I want to use the word you. If you're blogging that's fine but generally it's better to not do either so I'm breaking a habit. There are others too, and I am looking for them, as well as continuing to improve my grammar until I feel I have at least a journeyman's understanding of the craft of nonfiction.