I wouldn't consider beans to be OK. Beans themselves contain some carb but there are sugars in the tomato sauce as well.
I followed a low-carb diet for about 2 years, and lost 2 stone in the first sixmonths of that, which I kept off then through a high-protein diet and exercise. Unfortunately, I then slipped from the diet. However, I've recently started back and I've already lost 7 lbs. This however, is not just due to low-carb eating, I'm also exercising as well.
One of the keys to a low-carb diet is putting yourself through an induction phase. (This is common to Atkin's as well as the Idiot Proof Diet and others). In this you limit yourself to about 20g of carbs a day. This regime effectivly kickstarts your metabolism and once your weight loss is underway, you can start to reintroduce some carbs in a controlled fashion.
Carbohydrates are addictive and you will crave them when you give them up. But protein is extremely filling and after a period of about a week you will find yourself adapting.
I'll give you an example of what I would eat during the course of a day - this was yesterday's menu
Breakfast - Some cold meats, two pieces of cheese and half an avocado (Other regulars include a hard-boiled egg, a rasher, grilled mushroom etc)
Snack - a handful of peanuts
Lunch - A big salad of romaine lettuce, parmesan shavings, chicken breast, cherry tomatoes and a low-sugar dressing (I like salads, but somedays I will have grilled vegetables and meat of some form, or a homemade curry)
Dinner - salmon fillet served with a broccoli, leek and cabbage mix. This was followed by a small amount of homemade pate. (I also love home-made burgers, served with some bacon, cheese or egg)
Throughout the day I drank 2 cups of green tea and approximately 3 litres of water.
Atkin's diet book is worth a read. I know a lot of people think it's excessive, but there is some sensible advice in there too. He was one of first people I'm aware of to put forward the idea of carb-rich eating causing insulin resistance and sugar-craving. I used Atkin's first time out. I just modified the diet to remove half the frying he recommended.
Another diet book that will give you tips and pointers is India Knight's Idiot Proof Diet
. This is a low-carb diet but done in a more approachable fashion than Atkins.
Collins publish an excellent Carb Counter
book which gives you the carb content of everyday food.