We recommend hardware wallets like ledgers and trezors. Since all coins can't be stored on those, look into making paper wallets. Use walletgenerator.net.

Here are the steps:

Download the GitHub file to a brand new USB
Use raspberry pi with new linux os (no wifi or bluetooth capability)
Generate your keys
Print the keys with a wired printer
Send crypto to the deposit address


If you want it even more secure, put your private keys behind an individually serialized tamper resistant sticker. We sell coins that help with all of this if you want to learn more.

https://realcrypto.org/product/bitcoin-holographic-coin/

If you don't want to use a raspberry pi, you can use your computer offline. Just be sure to clear your printers memory and fully delete the files from your computer when you're finished and before you reconnect to the internet. It's not as safe as above but still a better practice than what the majority of people use.