What is the most effective way to quit a bad habit?

Find an alternative good habit: Replace smoking with fruits.

This is an interesting question. I think the only way to truly quit is to push yourself through the change - really promise yourself to stay strong and keep going, despite how hard the bad habit is calling you.

Cold Turkey and creating opposite routines. Ie: if you wake up late - force yourself to wake up early for 30 days in a row and you'll build a nice little habit out of it.