A good review on habits

Current Directions in Psychol Sci, Vol 15, Issue 4, pp. 198-202:
Habits-A Repeat Performance
ABSTRACT—Habits are response dispositions that are activated
automatically by the context cues that co-occurred with responses
during past performance. Experience-sampling diary studies indicate
that much of everyday action is characterized by habitual repetition.
We consider various mechanisms that could underlie the habitual
control of action, and we conclude that direct cuing and motivated
contexts best account for the characteristic features of habit
responding—in particular, for the rigid repetition of action that can
be initiated without intention and that runs to completion with
minimal conscious control. We explain the utility of contemporary
habit research for issues central to psychology, especially for
behavior prediction, behavior change, and self-regulation.