Important aspects of multi-sig
  1. Each signature comes from a different piece of hardware (hardware wallet or laptop or mobile phone)
  2. Best practice for no number of devices needed to spend, be on the same network (if on an network at all) so 2 computers are on different internets or not on the internet at all in a 2/3 multi-sig
  3. Do not physically connect devices together (Its good to keep signing computers from being on the same internet, its worse if they are connected via a USB)
  4. Verify the destination address on every device you use to sign (if a compromised device tries to lie to you, you'll know when you verify on a device that isn't compromised)
For even more hardcore security, check out glacier protocol: https://glacierprotocol.org/