Hey Cam, Everyone will have their own prefered method for targeting Jacks Lures, Livies etc. The best Jack I ever caught went 60cm on the good old handline with a live prawn, A few weeks ago I was smashed by a good Jack around 40cm in 6 inchs of water on a 3 inch Pumkinseed Gulp minnow, Then today fishing Tinny Creek I got belted and snagged up by a freight train using a $4 K-Mart rattler (best cheap lure I have ever bought by the way, Hit after hit until I lost it in the snag, will be stocking up)
Just do a search mate, There are so many guys posting about Jacks at this time of year you are bound to pick up a few pointers.
I just try and read the situation at the time and do whatever feels good to you, I find fishing is so much more satisfying when you just go with your gut instinct and give anything and everything a try.
Cheers Dave