thats up to yourself and you can get a lot of different opinions, some leave it 24/0 for the full veg stage. i personally dont, i find that 24/0 for around the first 2 weeks and then reduce it toi 18/6 works well. there are arguments that the plant need some dark time to grow, i cant give any real argument for or against but i tend to think that it may be correct. so after 2 weeks i reduce it and usually veg until the plant is at the height and size that i want it, always take into account that the plant will double and may treble when you flower it. be careful you have the room to accommodate this. most of us have ended up with giant plants that start taking over too much.