Get it out of the house!
If it's not around, it won't be a temptation.
When you shop for food, don't pick up the junk. Make sure you have a healthy snack in the car, so if you are tempted to buy some junk, you can tell yourself "I don't need that, because I've got my yummy X in the car I can eat."
Pick up some fruits. Their natural sweetness may help satisfy your sweet tooth in a health way (just don't add sugar to them).