As for WiFi, I won't turn it on. I like wire.
Amen, Greg. Wired is the safest way to go.
I have most of my devices wired to the router (and switch), but I do have one wireless IP phone so I kept the wireless transmitter turned on in my router. I also like for guests to be able to use their laptops when visiting, although I have wired outlets in most rooms for this purpose.
There's no doubt that the network should be set up with a unique SSID and password at a minimum. That alone will weed out the amateur hackers. John, remember that most of them are just neighbors who are too cheap to pay for their own Internet service. In those cases, your biggest risk is likely to be their surfing porn sites on your account. Still, you can never
be too careful with secure account information.
If you are comfortable with a fixed set of devices on your network, try to go wired. If that isn't practical, then next level of security is to disable the DHCP function of your router and give each of your devices (computers, printers, etc.) their own unique IP address. Without an IP address that YOU assign in the router, it won't talk to a stranger's computer.
If this is all more than you feel you can handle, it wouldn't cost much to have a local "techie" come out and set up the security for you. That would probably be money well-spent.