You might want to add fields to the record creation process in M-x bbdb-create. In addition to asking for name, company, e-mail address, addresses, phone numbers, and notes, you may want to make sure you remember to put in birthdates or other information. If you want to prompt for custom fields after the regular BBDB creation form, modify this simple example to suit your needs:
(defadvice bbdb-read-new-record (after wicked activate) "Prompt for the birthdate as well." (bbdb-record-putprop ad-return-value 'birthdate (bbdb-read-string "Birthdate (YYYY.MM.DD): ")))
Thanks to Kaleb Yilma for the question!