You can use Odoo's CRM app for this. Potential customers, in this case represented by business cards, are usually entered as a lead in Odoo. The tendancy is that you do not create a customer or a sales opportunity until you have qualified whether the lead is interesting or not.

When a qualified lead requires further actions, you can turn the lead into a sales opportunity and, eventually, a customer.

To make a new lead, go to the Sales > Sales > Leads menu and click the Create button. In the Lead form that opens, you can enter the contact data of this new potential customer and add notes. In the blue (= mandatory) Subject bar, type a brief description about the contact concerned, e.g. add more info about where you met the contact and how this person could be interesting for your company.

You can enter all contact data and even assign a priority to the lead. 

Note that the way the Address data such as zip, city and state are displayed, depends on the country set for your company in Odoo's Company Settings.

You can also enter business cards, i.e. leads for existing customers. Simply add the customer to the Customer field and related contact data from the customer form will automatically be added to the lead form.