First and foremost, there is no such thing as "spoofing" an ip address. All you can do is relay your traffic through another address. It is likely easiest just to buy some proxy services from a company that will give you options of where you want your address to be. Although if you were to do something illegal, and that person/entity wants to find you, then they send a court order sopena or whatever (i know nothing about laws). That company will then go back to their logs and see who was using that ip address at that time.
The best way is to either compromise someone else's computer or wireless network equipment. This way, that person is likely to not have logs of who was using their connection.
There is a third way, but i have no idea of where to start. There are huge whats called "botnets" which are slaves to their creators. They are leased out to people who want either computing power or bandwidth. This is the best way as you usually get lots of addresses. I have never sought out these services, and they are likely not cheap. You also run the risk of finding some undercover people or a scammed.
The easiest way would probably be to find a legit service mentioned above and use a disposable account of some kind. then using public wifi (or compromised wifi

) that has no real logs to connect to the proxy. Do not listen to people bullshitting about mac addresses. They are fucking retarded, as mac addresses are known to be reused and are in no way "permanent" for anyone that knows shit about hiding themselves. Although it is still a good idea to change it every time you connect.
You can also look into whats called a vpn. They are very similar to proxies, and are in fact almost exactly the same thing for this purpose. I would recommend ipredator myself. They only host in Sweden though. But they are stable and not likely to divulge you information. So they could be a bad substitute for an entry point to another proxy that would be located in the country/city of your choice.
And for fucks sake, DO NOT USE TOR. I beg you not to abuse that network, as it is really needed for people that want information behind oppressive government regimes.
If you need more info i would be happy to publicly supply it.