I stay below 50g per day, although I aim for under 20. 20 is the "induction" limit for Atkins. If you look at the primal blueprint recommendations (the carb curve) it says that anything under 100 grams is optimal for weight loss.
http://www.marksdailyapple.com/the-p...ate-continuum/
Honestly though, it's really personal. I do recommend though that if you're just now going low carb that you read up on "carb flu", which is basically the detox that happens when you go low carb. For up to two weeks you can feel lousy, but salt, magnesium and broth help a lot with that.
I always tell everyone to give it two weeks. Usually within a week I feel fantastic, even if I've been high carb for months.
Keep in mind that just by cutting out a lot of the junkier food and focusing on vegetables meat and fruit you can lower your carbs substantially (If you were eating that stuff before). This may work if you're less of a counter, more of a moderation person.