I quit without any support or anything but it was due to finding out I was pregnant so it kind of meant that the choice was taken away from me and I wasn't allowed to smoke! So, get pregnant! LOL
Seriously though, I have found in the past that I don't tell myself I have stopped smoking, only that I am not going to smoke today and that if I want one later then I can! I would give myself a time of say, 8pm, when I would allow myself a cigarette and then at 8 I would push myself to hang on for 15mins, then another 15, then another.... etc and before long it's bedtime and you have gone a whole day without one.
Don't get disheartened if you do snap, it's no biggy. Just start again. I also found it useful to keep reading over and over how and when my body was healing:
http://www.bupa.co.uk/health_information/asp/h ealthy_living/lifestyle/smoking/why/stop_text. asp
Good luck :-)