it's pretty easy to stick to under 20g of carbs, when you avoid all processed foods and eat naturally.
(generally sticking to veg that grows above ground, fish, meats + natural fats - i.e using butters, cold pressed olive oils, coconut oil + avoiding seed or nut oils)
It becomes second nature to avoid things with too much starch or sugar (like.. satsumas) and to opt for suitable options instead. Once you know what foods you have to avoid it's really not that difficult, and once you understand the science behind it, it becomes much easier to not miss those foods either!
I would suggest you read the atkins book if you would like to follow that plan, you may also want to watch something like this
The Food Revolution - AHS 2011 - YouTube
if you want to understand why startches and sugars are avoided.
If you do decide to follow a low carb plan, it usually involves eating higher fat levels, (eating high protein levels is counter productive, as excess protein will convert to glucose, raising insulin levels, which is what you want to avoid to lose weight via. low carb eating)
...so counting calories may restrict your choices (as fat is the most calorie dense food) - but it's the fat which helps lower calories, as it fills you up and satisfies cravings, helping to reduce overall food intake. So I wouldn't worry about counting calories, at least not in the first few weeks as you get into the swing of things. If your weight loss is unusually slow or stalling, THEN count calories.
