I quit in October of 2003. Best thing I ever did. In order for you to successfully quit, you have to be mentally determined with a reason why you want to quit.
My grandmother smoked her whole life, then fell and broke her back. She had to have surgery on her back, which was successful, but because she smoked her whole life, she was not strong enough to get off of the respirator. I watched my grandmother breathe through her neck for 600 days before she died a few weeks ago.
150 days (5 months) of watching my grandmother suffer made me mentally determined to quit smoking. Once I committed myself, fighting the urge was simple.
And the longer you go without a smoke, the stronger you become. If you give in and take one drag from someone's cigarette...you have just thrown away all of your hardwork and concentration. Be strong and never give up...
Also, this may help...everytime you see someone light up...in your mind, think the person is putting a cat turd in their mouth...pretty soon everytime you have a craving your mind will associate the cigarette as putting dookie in your mouth and the mental habit will be easier to break.
Good Luck!! You can do it!!