Not "You go to the desk." — say "Go to the desk.". 祈使句本来就是对 you 说的，所以把 you 省掉。
试一试: Ethan: I am hungry, and I have food in my bag. Maya: ___ outside. This room is for the class. 补全 Maya 的回答。 (Eat / To eat / Eats) 答案: Eat — Maya 是在让 Ethan 做一件事，这时就用动词原形，前面不加任何人。"To eat" 不是命令，而 "Eats" 这种形式前面必须有人。
否定：Don't + 动词
要叫别人 不要 做某事，就用 Don't + 动词原形。
Don't pay here.
Don't eat in the class.
Don't go in yet.
Not "Not pay here." — say "Don't pay here.". 要把祈使句变成否定，就在动词前面用 Don't，光用 "not" 不行。
试一试: Ethan: This jacket is nice. I have twenty dollars with me. Maya: ___ it now. It is much cheaper on the weekend. 补全 Maya 的回答。 (Don't buy / Not buy / Don't to buy) 答案: Don't buy — 否定的祈使句是 Don't + 动词原形。"Not" 不能单独放在句首叫人别做事，而且 Don't 和动词之间不能加 "to"。
加上 please 更礼貌
现在让语气软一点：在开头或结尾加上 please。
Please wear your jacket.
Go to the desk, please.
Please don't eat here.
试一试: Maya: Here is the money for the class. Ethan: ___ pay at the desk. It is over there. 补全 Ethan 礼貌的回答。 (Please / You please / Please you) 答案: Please — Please 单独用就行。"You please" 和 "Please you" 都在动词前面放了一个人，而普通的祈使句前面是没有人的。
Let's + 动词：提建议
想提议跟别人一起做某事，就用 Let's + 动词原形。
Let's go to the class.
Let's eat now.
Let's buy the books.
Not "Let's to go." — say "Let's go.". Let's 后面接动词原形，不加 to。
试一试: Maya: We both need the book for the class. Ethan: ___ buy two books at the desk. 补全 Ethan 的提议。 (Let's / Let's to / Lets) 答案: Let's — 提议两个人一起做事，用 Let's + 动词原形。Let's 后面没有 "to"，撇号也不能丢。
试一试: Maya: It is cold outside. I want to go home. Ethan: ___ 选出 Ethan 的回答。 (Wear your hat. / You wear your hat. / Wears your hat.) 答案: Wear your hat. — Ethan 是在告诉 Maya 该做什么，所以用动词原形，前面不放人：Wear your hat。"You wear" 在动词前放了人，"Wears" 加了祈使句从来不用的 -s。