Common Mistakes

It's not always true that if the main statement is in negative form, then the question tag should be in positive and vice versa, especially with imperative sentences. There are many points in English where traditional rules don't work.

• Do me a favor, will you? ➝✖️
• Do me a favor, won’t you? ➝✔️
• Open the front door, won’t you? ➝✖️
• Open the front door, will you? ➝✔️
• Shut your mouth, can you? ➝✖️
• Shut your mouth, can’t you? ➝✔️

Reason:

When your intention is to invite or request people politely to do something for you, you use won't you? after imperative. When your intention is to order or tell them to do something for you, you can use would you?/could you?/can't you?

However, if the imperative sentence is in negative form, use will you?

• Don't forget to call me, will you?

Note that we use "can't you?" to show some impatience.