Aha! Finally a post where I can be of some help around here, as my channel consists of pretty much all public videos, from interviews to pranks, and all kinds of in-between shenanigans.
When it comes to equipment, you'll want a wireless lavalier, you can find cheap but good ones on Amazon for about $40. The problem with this though, is that if you don't have a handheld recorder like a Zoom H1 or Tascam DR-05 (those are the brands' entry levels), then you have nothing to record into, so you'd need those to actually record the audio. So you would have one of these recorders in your pocket or something, with the wire under your shirt. So combining those two, at cheapest, you'd be paying around $110-120, roughly. Alternately, if you have an iPhone, Rode make some nifty wireless lavs called the Rode SmartLav which goes right into your iPhone, and that retails for about $80, so a bit cheaper (plus, Rode are a reputable brand). If you want to go further and have wireless receivers and whatnot, that'll be upwards of several hundred bucks, but if you're willing to spend that kind of money, then go for it, the quality will be great - we've been lucky enough to work with a couple of sound mixers that have equipment like that, and it makes it much easier than dealing with a handheld recorder.
Editing it together is the same as you would for any video, although you'll have to sync audio and video together. If you have an expensive wireless receiver that can transmit directly into your camera, that will save you that hassle, if not syncing is something you'll need to do, either with a plugin or manually.
Hiding a camera is surprisingly easy, depending on what type of video you're shooting. For the most part, we've had cameras not even well hidden, and people still don't notice them, just because they're too busy dealing with what you're doing to them. That being said, you'll want a zoom lens to shoot from far enough way still, and either a monopod or some kind of stabilization (if not just on a table or something), or it'll be quite shaky.
That's just the very basics of it all, I'm still new to it myself, but hopefully that kind of helps!