I am looking for some advice on linking Lookup fields together. Here is my scenario:

 

while creating a lead i want to have a Lookup Field labeled "Referred By". This field would be used to lookup and attach to the lead, a contact that referred them to my business. When the Lead is converted, I would like the "Referred By" information to follow over to the potential & contact modules.

 

How do I do this? I've researched but have been unable to solve my puzzle and i'm looking for some advice.

 

Thank you