Use the imperative form when giving instructions or orders. The imperative is also very common in written instructions. Be careful when you use the imperative, as it is often considered impolite in English. If someone asks you for instructions, use the imperative. If, on the other hand, you would like to request that someone do something use a polite question form.
There is only one imperative form for both 'you' singular and plural.
Examples:
Hurry up!
Take the first left, go straight on and the supermarket is on the left.
Positive
Base Form of Verb + Objects
Turn the music down, please.
Insert coins into the slot.
Negative
Do + Not + Base Form of Verb + Objects
Do not smoke in this building. Don't rush, I'm not in a hurry.
The words: at, by