IP address problems can be caused by a multitude of sources. Fixing a problem with an IP address first depends on diagnosing what exactly is wrong. Luckily for the technologically inclined, diagnosing IP address problems can be handled methodically.
The first step is determining what kind of IP address problem you are facing. Often times, your computer will tell you directly, especially in the case of duplicate IP problems (where two devices on the network are trying to use the same IP address). But what if your computer doesn't tell you what is wrong?
Most diagnostics can begin at the affected PC or network device. The first question you should ask (the user, or yourself) is whether or not the PC or network device worked before using that IP address. The second question you should ask is whether or not the PC or network device has a hard-coded IP address or one provided via a dynamic process, such as DHCP.
If the PC or device worked before, and the IP address is hard coded, double checking that the correct IP address is still configured is a good first step. It's a good idea to check that the net mask is accurate as well as the gateway address. Finally, verify that the correct DNS settings are in place. If you get this far, try to ping the gateway IP address. If you can ping the gateway but can't ping any further, you might either have a routing issue, or another network issue not related to the PC or network device in question. If the ping check works, but you still have intermittent problems, there could be another machine on the network using the same IP address. Verify this by checking the ARP table on the local switch (or asking somebody in networking to do this for you). If there's an entry in ARP with your IP address but a different MAC address, then another machine on the network has a duplicate IP address (relative to your machine). You could also have a problem with the network interface (card or port) or with the network cable connecting you to the switch.
If the PC or device worked before and the IP address is assigned dynamically (say, via DHCP), you can try releasing the IP address lease then renewing the lease (in the case of DHCP). If this does not fix the issue, there could be network problems preventing your PC from communicating with the DHCP server, or a problem on the DHCP server itself. You could also have a problem with the network interface (card or port) or with the network cable connecting you to the switch.
If the PC or network device never worked and the IP address is dynamically assigned (as in the case of DHCP) verify that there are no network issues or issues with the DHCP server. Check all the hardware (cables, network card/ports, etc). Attempt to hard-code an IP address not currently used on the subnet as well as the net mask, and gateway IP address. If this works, contact the DHCP server administrator or helpdesk and ask them to verify that the DHCP service is working.
If the PC or network device worked before and the IP address is hard coded, you have a harder problem to troubleshoot. The IP address could be wrong. The subnet mask could be wrong, as could the gateway IP address or DNS settings. After verifying that nothing is wrong with the network configuration (the routing, the switch, and the switch port. VLAN assignments, etc.), check the network interface (card or port) as well as the network cable. Ensure that the correct Ip address is configured, as well as the correct net mask, gateway IP address, and DNS information. Try pinging the gateway. If you cannot ping the gateway, try verifying that another machine on the subnet is working. If need be, try reconfiguring the other machine with your machine's IP address. Try to test each component or configuration against a known, working computer (or its equipment). If this still fails, try a different IP address on your PC.
The most important aspect of troubleshooting a networking or IP address problem is to be consistent while using a through methodology to attempt to diagnose the problem. That way your odds of missing a key diagnostic test or symptom and spending more time then necessary troubleshooting are lower, and your odds of successfully resolving the issue are higher.