What ever you lure selection is, the biggest tip I can give is to SLOW DOWN your retrieve. Barramundi are not Mackerel! For the most part they will size up a prey item for several seconds before engulfing it. Just watch one in a fish tank one day. If you pull the lure too quickly the fish will spook and turn away. I like to give a twitch of the lure and then count to 3 before twitching again. 3 seconds seems to be about the right pause time. Counting sounds a bit mundane, but when things are quiet its really easy to slip into simple 'cast and retrieve' repetition without realising it. And it just won't be as effective.