While this tutorial is primarily aimed at people who are new to building niche websites, those of you with some experience may find something useful here as well.
If you are starting with Affiliate Bootcamp then choosing your niche is easy. Your niche is promoting Wealthy Affiliate, and possibly some other make money online ideas as well. WA is definitely worth promoting, as the commissions are good, the product is great so you can write posts with authority and conviction, and the affiliate payouts are regular when you get some sign ups.
If you are beginning with the Getting Started training, where you learn all about setting up a niche website not related to promoting Wealthy Affiliate, then you will need to come up with an idea - a niche - that you can create an entire website around.