Many thousands of domains are cancelled each day. Most of the best ones are pre-ordered through specialist domain catching services. If not they are available to register by anyone, but here again many are registered within seconds of release. How to know when a domain is going to be cancelled?
Domain life cycle: (for .com .net .info domains)
1 Domain is initially registered for 1-10 years. Registration and expiry dates visible in WHOIS. Status is ACTIVE. Domain cannot be transferred for first 60 days.
2 If the domain name passes expiry without renewal registrar status becomes REGISTRAR-HOLD - the domain can still usually be renewed but may be deleted by the registrar at any time from 0-45 days after entering this state.
3 The domain will then usually enter the state REDEMPTIONPERIOD unless the registrar has sold the domain at an auction, or wants to keep it. So do not let your domains reach this point. This period lasts exactly 30 days and your domain can be rescued for a premium sum by your registrar only direct from ICANN.
4 Counting from the Updated Date shown in WHOIS after 30 days the domain will enter PENDINGDELETE for 5 days before being released. It cannot be rescued at this point and your only option is to use a drop catch service or take a chance that no-one will re-register it and wait.