I did a meal a day about 20 years ago when I was mid twenties... lost about 2 stone fairly quickly and recently started again (a few months ago - weight loss slower but definitely working). Working out an average after the initial water loss week I am losing 6 pounds a month, although I had 4 stone to lose on total and I am fairly inactive at the minute. I tried slimming world early this year and lost about 4 pounds a month on that.
I have been told by a dietician (that I know as a friend - not as a client!) that my eating would be considered disordered. I know some people feel the same so I wouldn't recommend anyone do the diet without researching it.
I always only really enjoyed my evening meal but wasted a lot of calories in snacking rubbish! It can be limiting at first, so many things you can't do like meeting friends for lunch or having afternoon tea, although technically you could change your one meal to earlier in the day - I always find it difficult to get back into the routine after a change like this though. I usually have my evening meal between 7-8, but always eat between 6-9pm.
I drink the odd cup of tea with almond milk (just because I drink almond milk - no specific reason!
Drink plenty of fluids during the day - you will be used to getting some fluids from your food that you won't getting anymore on this diet.
Pre plan your dinner so that it is a healthy meal and has enough calories, it can be easy to eat loads at the beginning because you are so hungry but over time it eases, and you do become quite full quickly.
Don't stock up on junk, and reward yourself with a lovely, healthy well-balanced meal. Not pizza and cake (although I have those days occasionally!)
Always check medications - some of them need you to eat first. My multi-vit requires a full stomach so I take it after dinner.
It was hard getting into it, I would say it took three weeks or so to stop feeling ravenous in the hours before dinner but once it was my routine it worked really well. Its working for me and I am fairly lazy so I'm planning to keep it up.