Fish 'em early, fish 'em late: Kings are more active in freshwater during the low-light, quiet hours. Plan your serious fishing for 9 p.m. to 1 a.m. and 5 a.m. to 8 a.m. (Remember: There is no real darkness in June or July.)
Watch the tides: If you're within 15 miles of the sea, you'll do better if you consult a tide book and fish intervals after the high tides or during incoming tides at or near river mouths.
Bad weather, good fishing: Cloudy, rainy days may be miserable, but fishing is always better then than on bright, sunny days.
Hot colors: Bring an assortment of the most vibrant fluorescent colors (orange, red, chartreuse, pink, etc.) you can find in flies, plugs, spoons, spinners, and drift bobbers, and change frequently until you find what's hot. Don't get stuck in a rut with what worked on yesterday's river or yesterday's conditions. Experiment!
Single and sharp: If you haven't already done so, replace all treble hooks with super-sharp, single or bait hooks (nos. 1/0 to 5/0). Check and sharpen your hooks frequently out in the field.
Get 'em while they're fresh: Try to fish kings no more than 50 miles from salt water if possible; they'll be brighter and more aggressive, and they'll give a totally undiminished account of themselves on the end of a line.
Keep it short: Use shorter leader/tippet lengths of four feet for all your sinking presentations on a fly rod.