Closed questions always start with a verb, the finite verb to more precise. While in English, we usually need an auxiliary verb (to do) to form a proper closed question, in Dutch we can do without. All it requires is inversion of the finite form and a question mark at the end of the sentence:
| Jullie staan meestal vroeg op
| You usually get up early
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| Staan jullie meestal vroeg op?
| Do you usually get up early?
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As you can see, the question is almost identical to the affirmative phrase. The only change is from jullie staan (affirmative) to staan jullie (question).
| Arjan is niet op haar verjaardag gekomen
| Arjan has not visited her for her birthday
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| Is Arjan niet op haar verjaardag gekomen?
| Has Arjan not visited her for her birthday?
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The above sentence is both a question and a negation. You can see that niet is situated between the middle and the right part: op haar verjaardag is a prepositional object, which sits at the beginning of the right part.
| Er waren geen getuigen van het ongeval
| There were no witnesses of the accident
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| Waren er geen getuigen van het ongeval?
| Were there no witnesses of the accident?
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Because the subject is non-specific (geen is an indefinite pronoun), we add the little word er. See also extra er at the beginning of a sentence. If we turn this type of sentence into a question, it is er that switches places with the verb, not the subject (geen getuigen).
Questions? 
