During Induction, no-nos include all fruit, high carb vegetables (potato, corn, peas, beans, etc.), all flour products (bread, pasta), rice and anything with sugar or fructose in them. (Read the book for a more comprehensive list.) What you can eat is most fish, chicken, beef, pork, salad greens, hard cheese and some other veggies. Once your body starts to adjust to this way of eating and aan extremely low carb level, you can go to the next level ("on going weight loss") and you start adding other foods that are low in carbs, slowly.
It is very easy to follow in the Induction strage - you basically eat salad (with full fat salad dressing) and meat. I found it to be very satisfying and easy to stick to.
As far as caffiene, it isn't recommended, but I drink lots of Diet Coke every day (my only sin right now!!!) and I have lost 82 pounds since last January, even after taking a month off due to surgery and three weeks off due to a wonderful lengthy vacation.
The main thing about Atkins I think is that is a life long eating plan - not a short term diet. I really like it, and despite taking "vacations" from the plan, I didn't really deviate real far (certainly did not eat like I did befor ethe diet) and getting back on track afterwards was easy and rewarding.
There are other benefits to Atkins, too, but this is already a long post, and I know many of our WISH colleagues will fill in more details. I hope you join us! Good luck!