Lainie...Joyce, Lisa, and I all started on the same day. I backup everything they have already stated. Days 2 - 4 were pretty rotten for me. I was cold, tired, and I had frequent headaches. After about a day I figured out a few tips which helped get me through to the beauty of when ketosis began and I felt wonderful again.
1) Make sure your supplements, meals are spaced properly. It is very important the first few days to be sure you're eating/drinking approximately every 3 hours. If I was late or skipped something the first couple of days, I felt awful.
2) Drink, drink, drink that water. I cannot stress how important that water was for me. The water helped keep the headaches at bay, and also kept my stomach filling full. The first few days I was probably drinking 100+ oz. a day as opposed to the minimum of 64 oz.
3) Make sure your Lean & Green (as Lisa hinted at) is measured properly. Remember that the allotted ounces of meat are based on cooked meat. You might also consider changing what time of day you have. Sometimes I have a nice grilled chicken salad for lunch if I'm feeling a bit tired earlier in the day, and then finish my supplements throughout the afternoon and evening.
I cannot say that these things work for everyone, but I know for me, those three things were key to getting through the first few difficult days.
Nancy said something once that gave me inspiration and that might help you along too....she said,
"Don't go through the first three days again. Do it right. Do it right now." She hit the nail on the head. The first few days are but one difficult part on the amazing journey to success you have started for yourself. Push yourself through it and you will succeed.
Congratulations on taking the plunge, and remember we're always here if you're in need. Good luck!