Domains are extremely cheap these days. So as a domain registrator, it is difficult to make some nice cash. But if you adopt the following technique, you might be able to make a good amount of money with minimum effort and time.

1. Find domains with non-working/incorrect email addresses that are registered with you.
2. Shortlist valuable domains from the above list. Look at the traffic, links and domain name value.
3. Ask your relative/friend to backorder the domain.
4. Send mails to the wrong/incorrect email asking the domain owner to correct his email address(!)
5. After 8 weeks, delete the original registration and transfer the domain to your friend/relative.
6. Profit!!!