How many times have you (or your students) played a passage perfectly at home, yet made errors during those times that matter...ie, in a lesson, performance or audition? It is human to err, of course, but secure tools to build consistent technique can lay the foundation for nearly flawless execution all of the time. To be confident about your technique, both accuracy and repetition are your best friends. It's important when you break a passage apart to GET IT RIGHT...this means articulation and dynamics have to follow the printed markings too...this is game changing for accuracy. As for repetition drills, there are many strategies: some of my favorites are to play a passage at a reasonable tempo, speeding up one mark on the metronome, then playing the same thing 2 notches slower on the metronome, then one mark faster, etc. alternating back and forth. I have great sucess by varying the rhythms, which changes the emphasis of finger combinations in a passage. Breaking the passage up into smaller pieces (ie, chunking) is also a terrific way to fix problems. Often it's only a two note finger combination that produces the stumble. Make every practice session a labratory for success, and try out these simple solutions for technical success.