Most of these suggestions are horrible, except for the two or three people who said cold turkey, because that's the correct answer. EVERY piece of research done on this subject has concluded the same thing. If you wanted to stop eating donuts because they're fattening, would you start eating cake instead? No, you wouldn't. So why would you use patches WITH NICOTINE IN THEM, the very drug you are trying to quit using? That's a very, very bad idea. In fact, studies have shown that most people who try to quit using those devices end up starting again, and the highest success rate is among those who just quit cold turkey.
I would personally recommend ramping things down, though. If you smoke 20 a day it will probably be very hard for your body to dive to 0 immediately without it having some pretty bad effects. I'd try a week of smoking 15 per day, shouldn't be that hard honestly. Another week of 10 per day. A week of maybe 6-8. A week of 4-5, etc.
I smoke sometimes, but I've never become actually addicted to smoking. I might smoke 2-3 cigarettes a day, or I might not smoke any. It doesn't matter that much to me, but a cigarette now and then can be enjoyable and has very little chance of causing any significant health risks. Although, doctors and many medical sources are trained to tell you otherwise, of course, for fear that your 2-3 per day turns into 20 per day. I've never had any problems like that, though. I just don't have the addictive personality nor do I have whatever it is that makes you become addicted to nicotine, which I don't find a very addicting substance at all despite the research.