It's a matter of willpower and good goal setting mostly, set clear deadlines and concrete, achievable goals. Rid yourself of as much distractions as possible. Very often the thought of having to do something is worse than actually doing it, keep that in mind. Procrastination isn't per definition bad, a certain amount of contemplation doesn't hurt big decisions. I just remembered another aspect, some have trouble suppressing their urge for 'instant satisfaction', this leads to fun before work. This seems like neurobiological component of procrastination.
