What tackle to use
8 to 12wt outfits, depending on the run of fish. Around structure heavier tackle is better. Generally 20lb and above tippet otherwise it ends pretty fast. When they are schooled up and surface sipping tiny bait it's advisable to use a lighter leader.
What flies to use
Clousers (both sparse and heavy weighted); Surf candies; Polar fibre minnows; Squid flies; Poppers; Crease flies; Gurglers
For surface feeding schools feeding on tiny bait, it is usually necessary to 'match the hatch' with small surf candies or eye flies otherwise things get tough.
When holding under white water on headlands they will aggressively hit poppers and large sub-surface flies.
Around structures such as channel markers and inshore reefs, kingies need to be excited a bit - large, long enticing flies such as weighted clousers, squid flies, and polar fibre minnows will work.
Kingfish are unpredictable and can change mood suddenly. If you can see the fish but are not having success it is always worth changing fly, angle of approach, presentation depth, or retrieve.
Teasing and berley (chum) works well at times.
Pulling a kingfish away from structure often requires special tactics. Mentally prepare yourself - if you get a kingie hit on a marker or anywhere near structure, one technique would be to take a wrap of line and hold on - 'give no line' - rod nearly flat at the fish and pull hard! A minimum of 20lb leader is required - more is better.
If the fish moves away from the structure keep steady tension and the fish will often just sit there for a confused moment - hopefully time to manoeuvre the boat away from the structure and have a clean fight.
Large kings will test every knot in your system and every drop of your patience.