if you are serious about security of your puter:
1) Do NOT use windows, use linux only. If you absolutely need windows set up a dual boot and never do anything confidential on windows
2) Learn to use partition encryption and use it to store anything confidential on all of your devices.
3) Never install any dubious software on your puter (including browser extensions)
4) Never access confidential info on an unsecure device (like any smartphone)
Excellent advice. I do not encrypt partition where the wallets are stored since the Electrum wallets are themselves encrypted, but 1, 3, and 4 are a must for me. I can add:
5) Learn to setup virtual machines (VirtualBox is free) and use them for experimenting with dubious software, including any new altcoin wallets.