Lips sliding is my favorite trick and it is so fun if you get it down. Just give yourself a little more room and speed to get your tails around while popping a little harder than you normally would. Just focus on driving those noses down after that pop. I like to picture myself backing into the rail until I feel it on my underfoot to get an idea for the feel. Then.. just level out your skis and grease it.
Once you get lips, try doing lip slides to back 2's. They're probably one of the "flowiest" and most rewarding tricks in the game, IMO.