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.
2. Don't store your funds in exchange for a long period of time. Deposit, trade instantly and withdraw.
well, but this make really hard to trade and use crypto!
Anyway, can someone tell me how is possibile to hack a dex like etherdelta?