When you're first leanring 180s, you should have the idea of a fakey pretty much down. You want to give it roll backwards, and what you're going to do is initially you're going to kind of compress so that you can get your bunny hop going your 180. You always want to lead with your head, so you want to look the direction you're going to turn. For me I turn to the left naturally, so as I go to 180, I compress, I begin looking that way, the rest of your body and your bike will follow right after. So once you're in the air, you want to kind of spot your landing.
Front wheel's going to come up, back wheel comes up, you should kind of be in your tuck position at about 90 degrees, halfway through you should already spot your landing, like I said you're going to be looking over your shoulder, spotting your landing. As you're coming down, you can either set the rear wheel down first, or kind of do both at the same time. As you land, like I said, you've got to have your fakeys already down, maybe a couple cranks backwards and, you know, you can go into full cabs, 540 cabs, fakey grinds, another great trick to link in and out of other tricks you got going on. That's pretty much how to do a 180.