Timing is everything....youve got to be there when the big fish are active and you cant spook them. Know your water. Pick a good spot and a good time to fish for them..High water conditions or low light periods are usually best for larger fish unless they are actively feeding.... Choose a fly big enough to keep the dinks off....Sneak up, and make your first cast count. Its hard to catch em if you can see them, especially if they are loafing on the bottom of a deep hole. Cheers.