Here's how you can think about it:
* Shape your mouth: Your lips should be slightly rounded and relaxed.
* Position your tongue: Your tongue should be high and slightly back in your mouth.
* Air flow: The air should flow smoothly out of your mouth.
Here are some examples of words with the long u sound:
* flute
* cute
* music
* pupil
* duty
* tune
* rule
* blue
Remember: The long u sound is different from the short u sound, which is pronounced like the vowel in the word "cup".