What are the methods of quitting?

There are many . . . 

"Cold Turkey". That world famous sudden cessation. The advantage is getting it over with. It is still quite effective for many, many people. 

"Gradual Tapering". Seems to make the most sense in that it addresses cutting down the level of craving before totally stopping. My own experience with people trying to quit is that it is one of the least effective ways. The commitment is to eventually stopping, and most people will go ahead and have an extra cigarette. 

"Cutting back" may sound like a very good idea, but actually probably doesn't do much to lower your health risks substantially. Most people go back to their previous levels rapidly. If it's a first step towards quitting that has a limited time frame (say, one month) with a commitment to stop after this, then it may be a useful technique for a very few people. 

Nicotine replacement therapy has a proven record of aiding in quitting. There are numerous forms available these days. There are two main types: patches (which provide a continuous supply of nicotine, aiding in losing the addiction to the "spike" of nicotine which occurs with smoking) and others which replace nicotine in "doses" delivered by gum, nasal spray, or other products. 

Antidepressants such as Zyban may be useful as an aid for quite a few people. 

Stop smoking clinics and programs, both commercial and non-profit are available. 

Self-help tapes and books (and this website) are available as guides.