The essentials
Self-custody means controlling the keys that authorize transactions. A recovery phrase can recreate those keys, so anyone with the phrase can generally control the wallet.
What to consider
Hardware wallets isolate signing from a general-purpose computer, but malicious approvals remain a risk. Verify addresses and transaction details on the trusted device screen.
Put it into practice
Store backups offline in separate secure locations. Test recovery with a small balance and never enter a recovery phrase into a support chat or website.