Bip39. Entropy values have to be sourced from a powerful source of randomness. This means flipping a good coin, rolling a fair dice, noise measurements etc. Never use phrases from publications, lyrics from tunes, your birthday or steet address, keyboard mashing, or anything at all you think that is random, https://directorylinks2u.com/listings13029359/bip39-github-https-linktr-ee-bip39-bip39-mnemonic-generator-an-overview