What tackle to use
6 to 9wt outfits, preferably LA reels with very smooth drag and plenty of backing when chasing larger fish. They have hard abrasive mouths that warrant the use of bite tippets.
What flies to use
Poppers; gurglers; crease flies; surf candies; deceivers; prawn imitations
The Giant Herring seem to turn up unexpectedly and not usually in numbers, but that really depends where you are.
Focus your efforts in tropical waters and warm water periods in sub-tropical zones. Fish tidal estuaries, bays and lagoons. Good spots will have deeper channels adjacent to shallow warm areas holding baitfish and prawns.
Bouncing retrieves to imitate prawn action while using sub-surface flies. With poppers, gurglers and creaseflies and other surface flies, a fast and jerky retrieve is usually most effective.