Pulling data from one form to another if basic CRM account? Is it possible?

Pulling data from one form to another if basic CRM account? Is it possible?

I have some custom fields I have setup that have been attached to all the forms (Leads, Accounts, and Potentials). I don't use leads but do you Accounts. I fill out the Account, which has several custom fields I have created. What I am trying to accomplish is when I fill out a Potential, is to have it pull the custom fields data from the Account. 

As an example:

Account - I populate the following
-Name
-City
-State

Potential - HERE IS WHAT I NEED HELP WITH
-Upon selecting Account
-I would like the form to lookup and populate the City
-I would like the form to lookup and populate the State

Can this be done????? I've tried everything but cannot get it to pull the existing account data. I have the fields visible on the Lead, Account and Potential forms but the data does not automatically pull through.

Thank you for your responses....in advance!!!