Before you do anything else, go make a list of every domain name you think you own. Include the ones which aren’t active, or which merely re-direct. Now look up the whois of each and every one of them, making sure that ALL the contact information is correct. And (assuming you still own the names you think you own), update any incorrect contact data. Next, go extend the terms of the names you absolutely can’t allow to drop. If you have just missed the renewal date, you have 30 days under the “redemption grace period.”
Remember, some employees, when they leave your employ, tend not to say to you “By the way, in one year, three months, the renewal notice for your valuable domain name will be sent to what by then will be my inactive email address.”
Maintaining domain names apparently is not that easy. It is my understanding that there is a certain large domain name company which offers portfolio management services. It drops so many names under its care that it has hired an outside company to act as a stalking horse to buy them back.
I used to think that an opt-in auto-renew policy would solve the problem of inadvertently dropped names, and I lobbied a little for that at the IPC. Verisign ignored the concept (it was proposing its Wait List Service at the time). One of my clients (a Registrar) explained to me another problem with auto-renew. The registrars would get killed on credit-card charge backs.
So the best procedure right now seems to be maintaining accurate lists of your domain names, and getting long terms for the valuable ones.