Ensure you change the default password for accessing the admin portal of your router and change the wifi password.  If you have the option, create a guest wifi access point and give that password to guests.

Most 'good' Internet Providers will have some kind of basic filtering, so if you try and access 'dodgy' websites, they should block you, but go a step further and use a DNS service that you can control.

This is a bit more technical, but a great idea is to use a cloud service to scan your public IP address for open ports, which could lead to vulnerabilities being expolited.