[plural subject] + 都 + [verb] / [adjective] [plural subject] + 都 + 不 / 没 + [verb]
都 means "all" or "both". It goes before the verb, and it refers back to something already mentioned.
Whatever 都 quantifies has to come before it. Dū都wǒ men我们shì是xué sheng学生 is wrong, and so is putting 都 in front of the thing it counts.
When the object is what is "all", it moves in front of 都:
wǒ我Dū都xǐ huan喜欢zhè xiē这些cài菜 does not say the same thing.都不 negates everything; 不都 negates the "all".
谁都, 什么都, 哪儿都 turn a question word into "every" – or, under negation, "none".
每 nearly always needs 都 to finish the sentence.