Always protect your wallet with a passphrase after installation. When you do, make sure to write down the passphrase so that you do not forget it in the future.
Backup your wallet.dat file after the installation on a secondary media such as a USB drive. This will protect you from any problems you may encounter in the future. If you send and receive a lot of transaction, you must make regular backups. You can backup your wallet using File/Backup menu.