..i would also add to the physical distractions the pp mentioned, that you ask yourself WHY do you NEED to smoke? what is the reason for you to pick the cigarette up emotionally, psychologically, what satisfaction it gives to you? does it calm you, does it make you focus your thoughts, does it make you take a mental break from the things around you, or are you a social smoker, or you smoke out of boredom or habit and so on...
also, ask yourself when are you mostly likely to light up? maybe make a little list of concrete circumstances and emotional states that lead you to smoke and try to find a pattern to it. this means noting both the time of the day (ie. after breakfast/meals/evening), location (at school/work/at home/with friends) and your emotional state (nervous/upset/bored..and so on)... soon you should see what leads you to the next cigarette the most, and once you know why, you can also try finding a strategy against it.
smoking is technically unnecessary. but it is an addiction. and like all addictions, besides the minor physical part (nicotine withdrawal), it has a strong psychological component, and becoming aware of it is the first step towards the real quitting. coming to understand WHY you NEED to smoke makes the entire act of smoking pretty senseless.