If it was me, I'd want to ask how the cable modem and PC are currently connected together - is it an Ethernet cable or USB cable?
How long has your friend had their cable modem? (If it's less than a year then it's very likely to be Ethernet)
Similarly, how recent their PC is, will also mean you don't get any nasty surprises when you turn up and find that their PC is so old that it doesn't have an Ethernet adapter built-in
In terms of routers settings that people haven't discussed yet, you'll want to change the following:
Change any administration passwords on the router.
For wireless, change the factory default SSID or ESSID name - for security reasons don't use a surname or other personally identifying word. Your ESSID is going to be broadcast for all you neighbours to see, and anybody else who is sitting outside the house with a laptop.
Set the wireless protection to WPA2 and choose a passphrase of at least 30 characters.
(You won't be able to setup the laptop end, but the passphrase need entering into the appropriate setup in Windows/OS X or Linux).
Obviously write down all of the above.