Buy a hardware wallet like the Ledger Nano S[1] or a Trezor[2] if you could afford it. This is pretty much one of the safest ways.

of if you couldn't afford it: Make sure you're always using the correct URL(myetherwallet.com/mycrypto.com). Type the URL yourself manually; not through Google search. or better, download the MyEtherWallet source code and compile it yourself.

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[1] https://www.ledger.com/
[2] https://trezor.io/