In the lesson on te/ta verbs we learned how to tell someone to do something. To tell someone not to do something you convert a verb into its naide form. To do this you add de (で) to the end of a verb in the negative form. Suru and kuru change into shinaide and konaide.
Don't read that = sore o yomanaide (それを読まないで)
Don't speak = hanashinaide (話しないで)
Don't do stupid thing = baka ni shinaide yo (馬鹿にしないでよ)
Kudasai can be added to the end to make the request more polite.
Don't eat the apple please = ringo o tabenaide kudasai
Another way you can tell someone to do something is using the nasai form of a verb. To convert a verb into this form you change it into the masu stem and add nasai (なさい) to the end. Suru and kuru change into shinasai and kinasai.
This form of verb is a more strict request/command, but it is not rude. It is similar to adding an exclamation mark (!) to the end of a request, but it doesn't express a raised voice.
Read your book = anata no hon o yominasai (あなたの本を読みなさい)
Drink water = mizu o nominasai (水を飲みなさい)
To turn the verb from into a more casual firm command you can remove sai from the end of nasai.
Go outside = soto ni ikina (外に行きな)
Eat your food = gohan o tabena (ご飯を食べな)