It is very important that the angler use flies true to pattern, and as tackle dealers are prone to substitution, and furthermore as different fly-dressers frequently turn out quite dissimilar flies under the same name, the angler should make sure that the flies he may purchase are correct in coloration, size and shape.
In a previous chapter something has been said of the manner of striking a rising trout when employing the slack-line cast as a preventive against drag. Other things being equal, success hinges upon the angler's ability to strike at the right time and with correct force--or lack of force. When fishing downstream with the wet fly, which the fish often takes beneath the surface, quick striking, at the first suggestion of the strike of the trout, is at a premium; it would seem that when casting the dry fly the strike should be timed just a bit slower in the majority of instances, although when floating the fly down a swift run one can hardly strike too promptly.
To avoid drowning the fly when fishing "up" in a fair current the line must be stripped in gradually and with the greatest care; at the same time it is well to take up every inch possible that there may not be too much slack to straighten out in the event of a rise. Striking should be done from the wrist and with strict avoidance of anything like a sudden jerk which will almost surely snap the fine leader if a heavy fish has taken the fly or possibly tear out the hook if the fish is hooked lightly; the motion should be smooth, swift and even, and it must cease at once when the barb has gone home.
As a rule when fishing with the dry fly the fish will be upstream from the angler when hooked. If possible keep him there. In the majority of instances the trout will bore upstream, or angle upstream to one side or the other, and will not turn and run down with the current unless roughly and carelessly handled. Nurse the fish along, exerting a constant but not too heavy strain, so that he will continue to fight upstream against the current, thus tiring more quickly; in other words, "play it safe." If by any chance the fish gets below you, "takes the bit in his teeth" and runs with the current, go with him. Wade if you can, but if this is impossible get out of the stream as quickly as you can and follow down along the bank. As soon as possible get the fish upstream from you again.