1- Knowing the expiration date.
Often you may forget to check the expiration date and your competitor is eagerly waiting for that D Day.
2- Keeping contact information up to date.
Dont let your expired mail ID become the reason for loosing the Domain.
3- Enabling domain security features.
Most domain registrars employ a feature called "domain lock" to prevent unauthorised transfer. Go for such a registrar.
64- Choosing a strong domain management password.
Ofcourse.
5- Registering your domain name as a trademark.
Or no body can relate you with the domain.
6- Reading every email your registrar sends to you carefully.
Ya they will contain the expiration notice also.
7- Consolidating multiple domains.
A backup strategy.
8- Registering domain name variants.
Dont let people go away due to mis-spelling or typing mistake. Your competitor may(must) gain.
So keep it safe.

