In addition to having a password for your wireless network, i recommend setting up few more obstacles, such as:
1.Allow only specific MAC addresses
2.Allow only specific IPs - or range
3.Limit wireless access based on day of the week or time of the day.
4. Manually open wireless access when you need it - see previous post here.
In order to configure any of the above, logon to your router's management page and go to Access Restrcition.
See below:
