When you make a guess and you want to get the listener's feedback, you add "do you", "are you", "won't you", etc. to the end of your question. Which one you choose depends on the verb that was used on the sentence:

You're from Tokyo, aren't you?

You went out to lunch, didn't you?

You won't leave me here, will you?

The rules for choosing the correction are:

1. If the verb is positive, the question is negative. If the verb is negative, the question is positive.
   You forgot, didn't you?
   You didn't forget, did you?
2. For most verbs, use "did" or "didn't"
   She made dinner last night, didn't she?
   Mark drove, didn't he?
3. In sentences that use "is", "are", "was", "were", "will", "have", "has", and other forms of "be" or "have", you match the question to the word:
   You've been there, haven't you?
   He's Asian, isn't he?

One other point - these questions can be pronounced as a question (when you're not sure about the sentence) or a statement (when you're more sure). For a question, your voice rises at the end:

She made dinner last night, ↑didn't she?

For a statement, your voice rises on the second-to-last word and then falls on the last word:

You ate all the strawberries, ↑didn't ↓you?

The example at the top should be pronounced as a statement:

I bet you don't remember me, ↑do ↓you?