Just want to reiterate what Isaac has said. I didn't actually sit the LAT, although I do UNSW law (got in just before they implemented it!). I know plenty of people who went into the LAT, thinking it was similar to the UMAT, and after getting their marks back thought Law was a lost cause. To their surprise, many of them got in anyway! Like Isaac said, whilst with the UMAT you're looking for a crazy high mark, with the LAT it's more like meeting a 'threshold' (ie. Are you sorta good at writing/being persuasive? If so, you're all g on the LAT front). If you got a brilliant ATAR, I sort of doubt that the LAT will play into it at all. If you get a great ATAR, they may look at your LAT mark, and if you got a 'below cut-off' ATAR they might begin to take your LAT result a bit more seriously. Basically, don't stress, it isn't a big deal, and you can't prep for it. Don't expect a high mark, because no-one gets one.
Jake