Digital tuner
A digital tuner is a great tool for training the flutist's ear to hear pitch and determine whether notes are sharp or flat. When I was in high school, tuners were big, clunky boxes that you only used at school. We all tuned our instruments to B-flat before band started. No one had one at home--they were too expensive. Now everyone has a digital tuner--maybe two or three. One at home and one in the instrument bag. They are very affordable, under $30, and if you purchase a combination metronome/tuner, you have a music studio the size of a cell phone.  
What's the best way for a flutist to use a digital tuner? A tuner is just a great tool, but it doesn't magically tune your instrument. You need to use it on a consistent basis. With continued use, however, your ear becomes more adept at hearing flat and sharp pitches. Of course, you can use it for the "tuning note" - B-flat in band and A in orchestra - but each note needs to be played in tune as well. Just because one note is in tune, doesn't mean the rest of them are. An effective way to use a digital tuner is with long tones. Leave the tuner on while practicing them and watch the indicator. If your pitch goes sharp in the high register, relax your embouchure. If you are playing flat in the low register, make sure you have a strong air stream and direct the air up toward the ceiling. Some musical snobs decry the use of tuners of any sort. Students need to use their ear, they say. For flutists who have no concept of pitch, the tuner is a great aide for developing one. There's an old joke about instruments being tuned at the factory. Without the use of a tuner, though, most students' instruments are never played in tune again once they leave the factory. Over time, a flutist can develop an ear for proper intonation, but it doesn't just happen on its own. Digital tuners are a valuable educational tool. Get one and use it! You can even download a free digital tuner here.
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