I'm 30 and have been smoking since I was 18, how can I quit?

Like any addiction. You need support from a 12 step program, smoker's anonymous, and perhaps a trial of chantix.
Various Options. There are a number of options for quitting that you should speak with your family physician about. A lot of people try quitting cold turkey, which is extremely difficult. There are some pharmacologic treatments, including buproprion and chantix, as well as nicotine gum. It's important to remember that slipping back into the habit is common and can be overcome with social and medical support.