You can use the waiting list section to add members that are not "proper" members yet.
Go to "Members > Waiting List" to view and add some.
To add custom fields to your waiting list, first create a custom field group and add some fields.
Then, go to your Club Details page under the Setup menu and select that field group in the Waiting List Custom Fields field.
When you view your waiting list form on your website, the custom fields will be listed at the bottom.
Also, when you view someone on your waiting list, the custom fields are listed at the bottom. Click on the data to edit.