Use the smallest hooks you can find and bakers dough for bait, just enough to cover the hook. They are very finicky and easily spooked so light lines are needed.

 and just cast at them as they r swimming past or use a float and just wait?

 Another way is to use a jag hook with a running sinker and cast over a school then rip the hook through.

probably illegal ?

 For jagging fish? How? I'm sure everyone has jagged a fish before? 

caught them on rump steak before not sure if it was the white fat or the red meat that they liked

that was with a star on the bottom with small hooks , double drop

Throw net

 When we were grommets we used dough or red meat behind a blob with bulk berley.

get them in the berley and they,ll eat the dough

It has a V entry. Fill it with some bread and throw it into the shallows of an estuary etc. Dont forget to tie it off. Mullet swim in but cant easily get out. Works well on the East coast, havent had that much luck here.

With a mixture of finely minced mince meat, semolina and curry powder ( a good one - Vencat works well) - squeeze the mixture into a weighted burley spring with tiny hooks above and small pieces of cockle or prawn I do not know why it works but it does and really well  ! 

I have herd that people get them on fly now and again. no trapping allowed in the river.

Hi.

I've discovered an excellent and fun way to catch sea mullet with few dramas. I fish the Swan River, Perth, WA. I generally target black bream and bar tailed flathead in season, however, I discovered a means of catching the large sea mullet that inhabit the river all year round. The fish get up to and slightly over 3 kilograms and are excellent table fare when prepared the same day. They are tremendous fighters on the light gear I use for lure fishing bream and flathead, from shore or wading. My lure collection is extensive and I use lures only. Using bait - of any kind - is impossible due to the blow fish that also inhabit the river. There is one and only one lure that the mullet will hit, and they hit it nearly every cast when they're active, even in just a few feet of water casting from shore. The lure is a hard body Zoea 49S shrimp. The colour I use is glassy green, which very closely resembles a river prawn. The mullet hit it with gusto, but not in a predatory way as you might first think. They 'bump' the lure, flicking at it with their tail and knocking at it with their head. As a result of this they are regularly foul hooked and able to be landed (after quite a fight!). The hooks generally embed themselves either around the head, or in the tail. The standard hooks on the Zoea shrimp are far too small for jagging 3kg sea mullet, so I simply replaced them with larger, S-Owner brand trebles (size 10). In 30 minutes of fishing, when the fish are active, I'll generally land 1-2 fish around 3kg each as mentioned, with many, many more strikes and near misses. I use a light 7' Team Daiwa-X rod mated to a 1000 series Shimano Stradic CI4+ reel. Line is 6lb braid and I also employ 60cm of 10lb fluorocarbon leader, a tiny black crane swivel and a small black clip to facilitate quick lure changes when I'm fishing for different species. The decade of experience I've accumulated fishing the Swan has shown the swivel/leader/clip rig to work best for my purposes. The lures I use, including the Zoea for mullet and other lures such as the EcoGear VX-35, are very light and require light tackle such as I've described to get any sort of decent casting distance. I use a slow, 'bouncing' type retrieve, keeping the lure off the bottom to avoid sea weed. So that's the experience I have with sea mullet, and they're definitely worth going after in any manner as they're excellent sport and table fish, and at 3kg, there's plenty to go around! I hope that this helps. I've tried to put everything down that I could think of but if anyone has any questions I'll be happy to help - just message me and I'll get back to you when I'm able. Tight lines! :)