Over and above backing up your @mnemonic-seed so that you have access to your account in the event of critical data loss, it is also important to practice good security. Use a secure password when creating a local Monero account (not used on [MyMonero](https://mymonero.com) or other web-based account systems).
Don't ever give your Monero account password to anyone, as this can be used to access the Monero on your computer without knowing your @mnemonic-seed. Similarly, make sure you have running and up-to-date antivirus, especially on Windows computers. Finally, be careful when clicking links in emails or on unknown and untrusted websites, as malware installed on your computer can sit and wait for you to access your Monero account before taking the funds from it.
Providing access to your Monero account to your next of kin is just as easy as it is to backup your Monero account. Simply leave your @mnemonic-seed to them in your will, or store it somewhere safe where it will be given to them upon the execution of your will. A key advantage to this is that your next of kin won't have to wait for months for a third party to release the funds to them.