I see where many recommend that if a lifter reaches a "plateau", he should quit that exercise and find a new one for the same muscle. To me that seems very ill-advised.
Any lifter who's NOT keeping a notebook, and writing down the resulting reps in every set, isn't very serious or knowledgeable about weightlifting (or at least not using all the available tools).
To constantly "challenge" your body to do at least one more rep than you've ever done before at the same weight---is a huge motivational factor for gaining strength. Once you have a baseline of gains, you have a target to aim at every time. You're then able to build up the proper level of intensity to work right through any "plateau" and keep gaining. Changing routines defeats this motivational factor. Sure, you'll make nice gains for a time after switching, but that's because you've regressed so much in your starting point for your new routine---you're a beginner again, as far as the pertinent muscle is concerned.
All lifters should find their ideal exercises early, then stick with them, constantly building upon past gains.