Hi Murali,
Thanks for your answer, but that isn't exactly what I'm trying to do. I know how to use field merges and they typically work very well. What I'm trying to do seems a bit more complicated than just using field merges.
Our event staff would love to enter into a form the email address of a contact that they spoke with at a tradeshow. Email address would be the only field on the form. After they submit this form, a different form pops up on the next page. This new form would be pre-populated with all the information (in certain fields, not all fields) we know about that contact, IF they are a known contact in Eloqua. Then the event staffer would only have to fill in the fields where we didn't have information on record. If they were a new contact, the form would be blank.
Any other ideas for how to accomplish this?