Define best? Most secure: WPA2 with AES. Technically WPA Enterprise but that is very very complex.
If you have a mixture of old and new PC's on your network, then WPA/WPA2 with AES/TKIP security is the way to go. Anything above XP SP2 should be able to connect and still allow the option for the more secure AES. You don't have to know what any of that means though, just try WPA2 with AES and if that doesn't work, report back. Good luck.