I hold mine down while moving it towards the mouth. So just slightly before, but that all depends on what you like or not. The "crackling" sound is pretty much the juice boiling. In an electronic cigarette, the juice is a special type of heat resistant string known as Silica. A heating coil wraps around that, and when you push the button, it starts boiling the liquid in the wick. That's a typical ecig setup. more advanced and hobbyests use a big batteries, big atomizers, and replace the silica with cotton. So, if you see posts referring to those, you'll at least know a bit of what's going on.
I hope that helps.
