To sign the word “have” appropriately depends on its meaning. 

Have (things)
Have (acted)
have no
Have not 
Have to
Have been

Examples
have (things)
I have a box. 

have (acted)
I have seen you before. 

have no
I have no food. ​

have not
We have not met. 

have to
They have to work. 

have been
I have been reading.

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​Note: For questions with “have," make sure to sign “have” right before the verb. For example, for the sentence, “have you seen me?”, sign this way “? you have seen me?” instead.