camb1988 is spot on with catching yakkas. Burley is key and bait jigs/ sabiki jigs are cheap and effective.
If you do a search on this site for catching poddies, there's plenty of info in previous posts, but here's a quick summary of what works for me...
I've used both the expanding mesh net type of trap and the clear plastic cylindrical type and both types work. I mainly use the clear plastic type as all my mesh net types have failed in the zippers after a few months. The homemade traps are also effective. In terms of spots, most sand flats seem to hold poddy mullet as do areas around boat ramps for some reason. Burley up with some bread first to assess whether you've found a good spot. If you don't have a school of poddies fighting over you're burley, move on to another spot.
Place about half a slice of bread in your trap and then place your trap in the shallows. Thoroughly wet the other half of the slice and mush it into a milk slush. Sprinkle the milky bread around your trap as burley. Some people will tell you to put it 30cm or so under the surface. I'd disagree... In my experience you catch more when the opening of the trap is just under the surface. I find I get far more, far sooner this way. My observation is that they generally swim in the top 15cm of the water column and they're reluctant to swim into a trap any deeper than this.
Good luck ! The poddies are dynamite on flatties!