So by eating healthy fats, proteins, and veggis, you keep yourself firmly in ketosis. Also, to add, in this thread, Paleobird has talked about how eating too much protein pushes her out of ketosis, so this concept is also something worth thinking about. If I understand correctly, Paleobird tries to keep her ratios to 70% fat, 20% protein, and 10% carbs. this keeps her firmly in the ketosis zone.
Hope this helps.
Edit: For me, I know I'm in ketosis when my cravings go away. Silly, I know, but in the past few days as I've upped my fat content (and have still kept my calories down), I don't crave things like I used to. Also, I mentally feel like things have leveled out, I feel a contentedness. It's weird, I know.