Shortest answer I can give you, start with a place that reasonably well known and legit. You're just getting started as an author. That means you're going to have to work for free or for short money to start. Then, when you get established you can make the huge bucks that an established writer makes.

And yes, that's a GIANT joke. There's very little money in technical writing. You're primarily writing for recognition. But, that's all the more reason to go to established locations to get published first. Writing for SQL Server Central is a great way to get started. They don't go into really heavy edits, so the process is reasonably painless. It'll let you get your feet wet and decide how much you want to do.