The best tip for the first week is to stick with it! Don't give up or give in
The first week is pretty rough, but you have to keep pushing through to get to the other side.
Drink lots and lots of water. And don't be afraid to have 4 or 5 packets if you are hungry. If your coach allows restricted items, make sure you only have 1 per day. Eat your veggies. Lettuce is unlimited so make a huge salad! It will fill you up.
Again, just stick with the program. You will probably feel hungry, tired, headachy and tempted to say "forget it". Just get through it and once you are detoxed of carbs and in ketosis, you will feel so much better.
Oh- and stay off the scale. Do not stress how if you are losing, how much you are losing etc... Just wait until WI day and have faith in the program.