If you wish to record notes on a general conversation you could add a popup note during or after theconversation.
Open the Customer record, then select Popup Notes, then click New Popup Note and enter the text as appropriate.
If the conversation leads to a specific enquiry then you can again open the Customer record, select Enquiries, then New Enquiry and then add the enquiry and perhaps Schedule Follow-Up Call/E-mail as appropriate.
This will also allow you to search for Enquiries in the Customer Search Wizard.