1. Use a hardware wallet. If you can't afford one, make sure your PC is clean and use an open source desktop wallet (e.g Electrum) that give you control over your private keys.
This, and actually write down the seed on a piece of paper. I can't believe how some people actually buy hardware wallets but save their seed on a .txt/word file or their mobile phone's notes app. I can't believe how people with 6-digit portfolios be THAT careless.