You can generate a custom report of registrations using the report generate tool (Members->Player/Parent Reports->Report Generate). On the report generate page, there are several options for reports that can be generated. For a registration report, for the report type, choose "Registration".
Once you've selected "Registration" as the report type, the registration report options will appear. From here you can choose a season and registration status (the registration statuses are as follows: registered, tryout, withdrawn, and waitlisted).
Additionally, you can choose which fields you would like to appear on the report. Click one of the links in the field selection section, and you will be shown the fields that are available to be placed on the report. Custom fields will be included in this section, and can be placed into a report just the same as the standard fields.
Once you've clicked "Generate Report", you will be brought to a page with buttons reading "Export to .csv" and "View Report". Clicking one of these will allow you to export your report as a csv file or view the report within the web page, respectively.