first off, don't quit in the middle of the day where you've smoked already. start off a new day without smoking. don't quit unless you absolutely want to. it won't work if you're not doing it for you. also, once you decide to quit, don't try to convince yourself that you've changed your mind 1-3 months into it.
try nicotine patches, which you can buy a two week supply of generic brand at walmart for $30 (which worked great for me, kept my cravings to a minimum, but where i screwed up was thinking that i was doing so great that i could skip steps and go to other steps early. start the patches and stay on them all day for 6 weeks per step, 18 weeks total for most, whatever the box says) and figure out something to keep your hands occupied. whatever you do, don't replace smoking with eating. i did and gained about 30+ pounds in three months. try to replace smoking with drinking (tea, water, even coffee - its much easier to kick caffeine than nicotine so that later on when you're ready you can just switch to decaff and be done with caffeine by the time your body realizes what you've done).
talk to your friends and family and let them know whats going on - they'll be happy to deal with your crankiness and bad mood now as opposed to you dieing of cancer later. you'll find an amazing amount of support from friends and family, and they'll be glad to help, even to lengths beyond what is tolerable, into what is downright infuriating. that's why you need to tell them from the very beginning exactly how much they can help and at what point their help is no longer constructive or wanted.
personally, i wouldn't bother with the nicotine gum, because it only helps when you have cravings. treat the addiction to the action of smoking first (which is the hard part); the patches work by giving your body a constant supply of nicotine at all times so that you don't *need* to smoke to get it, and once you're clear of the addiction the the act of smoking itself, beat the addiction to nicotine (which takes 48-72 hours and 4-8 tylenol to overcome).
if that fails, you may also consider talking to your doctor about treatment with wellbutrin. in any event, stay strong, take it one craving at a time, and just keep living your life. best of luck to you!! PM if you need any help or encouragement.