Short-oo is a vowel that is a little bit unusual. Now, you may be thinking, “But that’s not a letter in the English alphabet!”, and of course, you’re right. But Long-OO and Short-oo is a pair of vowel sounds that follow some of the spelling and pronunciation patterns of the other Long and Short vowels of English.
How to pronounce Short-oo
Just like all of the Short vowels of English, a key factor to pronounce it well is to relax your tongue. Start by saying the Long-OO (Long-U-2) sound: “OO”. Then, hold your tongue up in the same place, but relax it completely: “OO” > “oo”.
Also, your lips should stay rounded — Short-oo is the only Short vowel with rounded lips.
Be sure to relax your whole tongue, all the way to the back, because there are some words with Short-oo that could be confused if you don’t relax your tongue. Here are a few examples:
Short-oo — Long-OO
could — cooed
hood — who’d
look — Luke
pull — pool
stood — stewed
would — wooed
Common Words with Short-oo
This vowel sound is a little bit unusual in some ways, but it is used almost as much as any other English vowel sound, because there are several frequently used words that have it. Here are some of them: could, should, would, put, push, sugar, book, look, cookie, hook, took, good, wood, stood, foot.
One fun way to practice the Short-oo sound is with the tongue twister “How Much Wood“.
PronunciationCoach 
What sound is it when oo is in book, look, cook, shook?
Short-oo.
I am a little dismayed at the information available for the oo sounds. There are clear differences when oo is followed by; k, r, l and d. Although the d is also in the true long oo sound, food, other words, such as blood and flood, clearly say the short u sound. I have been looking for words that demonstrate this, so I can try to find a patern.
There is not a super strong pattern here, but most words spelled with “OO” will use either the Long-OO or the Short-oo sound. Words that end with “-OOD” are not predictable. They basically form 3 groups: Short-oo (good, hood, wood, stood), Long-OO (food, mood), and Short-u (blood, flood). In this case, the total number of words involved is not super big, so it is easier to memorize them. One factor involved is the fact that many of these are frequently used words, and the most frequent words have a higher level of irregular spellings.