Backups
Many people have lost their bitcoins due to computer crashes, physical device loss, or theft. Even if you are using a secure wallet, you need regular backups of all your wallet.dat files. Consider storing your backups in several secure locations, such as on a different hard drive, on a CD, and a USB. Provide strong password protection for all private key backups.
Updates
Keeping your wallet software up-to-date is an essential protection measure against hacker attacks. Always make sure you have the latest wallet software version for an optimum security protocol.
Multi-signature
A multi-signature setup can significantly limit the danger of cryptocurrency theft. Multi-signature means that several reliable, pre-elected users must approve a Bitcoin transaction before it takes place. Thus, if one of the servers is under cyber-attack, the cryptocurrency is still safe, thanks to the other servers.
However, as Bitcoin.com states, using multi-signature means 'you have to trust another party,' so use this measure wisely.