You can use a jet lag calculator like this one: http://www.britishairways.com/travel/drsleep/public/en_gb
Alternatively, just decide how many days you'd like to take to adjust your sleep schedule and divide the number of hours you need to change by that number. Example, I want to go to London, which is 8hrs different and I'd like to start adjusting 4 days before my trip so 2hrs per night!
Any time its dark in your destination city, you should be avoiding light. Wear sunglasses or your sleep mask. Any time its light, you should be seeking light. Turn all the lights in your house on.
Take the melatonin a couple hours before you would like to go to bed for the night. It gets your body believing it's time to go to bed.