ethtool is the tool of choice here (give credit to Shadur), it'll let you know if you've got a link, and if you somehow got a half-duplex connection or some other misconfiguration.
If you don't see anything in the syslogs or in the output of
dmesg, then you might be able to increase the debugging verbosity of the network driver. Try running
modinfo -p e1000 (replace "e1000" with the name of the driver for your NIC). There might be an option you can give to modprobe (or put in a file in /etc/modprobe.d/) to increase the verbosity or debugging information.
Also, check out running
tcpdump -i eth0 as root (replace "eth0" with your network device). You can see what kind of traffic you are getting, even with the interface unconfigured. You'll see stuff like broadcast or multicast traffic, and possibly your system's attempt to DHCP.