Some people reach ketosis faster than others. Both your liver and mucsle cells will need to be depleted of their stores before the body switches to ketones for fuel. This can take as little as 48 hours to one week.
If after one week you haven't experienced the effects of ketosis, check your diet for hidden sugars. i.e., sauces, creams, marinades, etc.
The body goes into a state of confusion for the first few days as it attempts to adjust. Sometimes nothing happens for 3 days then Boom!!!! It happens.
I would keep carbs very low for the first week to allow you to make the metabolic shift of being a sugar burner, to becoming a fat burner. Thereafter, you can increase your carb intake a little each day, or a lot on a cycle. i.e low carb during the week, high carbs on weekends. Or my personal favorite, allowing one carb load every 3-4 days. Also, make sure you are facilitating ketosis by consuming plenty of water throughout the day.