You already have! Sounds like you have made the decision you want to quit, this is the first step. Things that can help solidify your decision is making a list of the pros and cons of this habit, how it affects your health, how it controls your daily life, etc. Next i would recommend talking to your doctor, medications can help with cravings, as can nicotine replacement therapies. Focus on exercise and healthydiet.
Set a quit date. The first step is to truly want to quit, and the best way to show that desire is to set a date. Preparation by cleaning the house, laundering or dry-cleaning curtains and rugs, removing ashtrays from home and car, telling your friends, esp your smoking friends (ask them not to give you tobacco, even if you ask) are some of the preparations you can take. Smoking cessation programs help, and meds.