The whole subtle body system revolves around the central channel. Once you get a feel for that, you can branch out and feel the two side channels, and eventually all the smaller nadis that run throughout the body.Some people however have a difficult time sensing their subtle body at all. A good technique for getting the feel of the central channel is to drink a glass of water and take a piss at the same time. You get the sensation that the liquis is moving right through you, even though of course it is not. The channel that your imagination using to create the sensation is the central channel. Get the feel for it using this excercise, than recall the sensation in deeper meditations.