What are some effective ways to correct a poor sleep schedule?

Sleep Hygiene. To correct your sleep schedule takes time. You need to set a sleep schedule and then stick to it. Go to bed on time, get up on time. Remember that the bed is for sleep and sex, not homework, tv, video games, etc. If you don't go to sleep after 20 min, get up, move to another room and do something boring for a while till you get sleepy. This will you help get your schedule reset.
Regular schedule. The 2 most important things in setting your body's sleep-wake clock are to 1) get up at the same time every day regardless of how much sleep you got, 2) go to the bed at the same time every day. Setting an alarm for 30 min before bedtime can be helpful.