It depends on what the sentence would look like if you phrased it as a statement rather than a question: in particular, what is the main verb, and whether there is a modal / auxiliary verb (must, will). 

For sentences with a modal, you simply move the modal to the front:

> You **will** need a car<br>
**Will** you need a car?

If there is no modal and the main verb is **be**, you move the main verb to the front:

> This **is** your hat<br>
**Is** this your hat?

If there is no modal and the main verb is not **be**, you add **do**, and convert the main verb to a bare infinitive:
> Your company **works** on PHP?<br>
**Does** your company **work** on PHP?

**have** is complicated, because it can be either modal or not.

> You have seen him. -*modal*<br>
Have you seen him?<br>
<br>
You have got a car - *modal*<br>
Have you got a car?<br>
<br>
You have a car - *non-modal*<br>
Do you have a car?<br>