Yeah, I started slacklining too this year, I remember mentioning it already in one of your MA posts. It's good fun, especially after a couple of beers at a BBQ for an added challenge

And hopefully some of the balancing ability will also translate into better skiing. I got the basics down after a few weeks or a couple of months, like crossing a ~10m line, turning, hopping onto the line. It definitely goes away if you don't practice though; after about a month of not practicing, it took me a few sessions to come back.
I don't really have much wisdom to share technique-wise. I also didn't take video (I know, bad). The only thing that I deliberately worked on was hip "counterbalance", i.e., working on keeping the hips level or slightly tipped towards the stance foot even. Other than that, was just trying it over and over again and playing with it. It was really hard to get going, the first sessions I would celebrate getting past 2 or 3 steps, but after a while it just clicked.
I'd like to learn how to mount the thing properly next, so far I've always started close to the ground. If I can get that down, I don't know, maybe I'll buy a longer line (I got a 15m one) or maybe try a different kind of line (I got a Gibbon classic now). Ideas?

And yeah, if you're thinking of buying a line, I'd recommend getting a longer line - the extra slack is a bit more work to set up when you start with short distances, but you might outgrow a short line rather soon, the lines are generally not extensible, and for some reason, they don't really seem to sell the webbing separately.