Securing your own WLAN/Wi-Fi infrastructure is very important. Unsecure connections can easily be hacked by unfriendly hackers or the whole traffic can just be sniffed and so they'll get your account credentials i.e. for your online banking.
There will never be 100% security for wireless connections but with some easy doings you can secure your Wi-Fi:
- Set your whole infrastructure to WPA2
- Choose a secure password
- Activate the MAC-Filter on your router
- Deactivate your Wi-Fi/WLAN when you are not at home/night
Again, this will not make your infrastructure 100% secure but you can avoid script kiddies to get into your connection.