I fasted for 4 yrs (18-20 hrs a day) 6 days a week......Felt great, had plenty of energy and slept soundly every night. Two yrs ago, I moved to NOLA, quit fasting and going to the gym. It's been fun down here but it's come at a cost. I'm taking this month to work my way up to 18-20 hr fasts.
Start by trying to fast for 10hrs. Eat a healthy lunch, some mixed nuts in the afternoon if you feel you need something to carry you till dinner. Eat a healthy dinner (by 6pm if possible) and then drink water at night when the hunger pangs hit. No coffee unless it's straight black. Even in the smallest amounts, creamer, sugar, Splenda, etc. will break a fast. Wake up in the morning and if it's been 10 hrs and you're hungry then eat but if you can push yourself to hold off for 11-12 hrs then do it. Just progress from there. After a while, you'll get to where you'll wake up in the morning and not be hungry. You'll be at 16 hrs before you know it then 18. Lunchtime and dinner with something healthy in the afternoon then you're set.
The key, early on, is to not break fast when the pangs hit.