The first few days are the toughest so you can get ready by:
--reduce your carb intake prior to starting
--you can start setting up your My Fitness Pal food tracker now and take all your measurements etc. so you have your real starting weight and measurements before you lose weight
--Starting to drink more water is just a good practice.
-- I also gave up caffeine, so if that is something you might want to do, you could start weaning off that
-- get your vitamins organized and the stuff you need ready -- a good kitchen scale etc.
Don't worry about "round numbers"... honesty is better and a lot of us started losing weight before IP. To me, that counts in your weight loss journey. Your healthier eating can start any time before June 1st
Welcome to IP -- good for you for making a plan. That's already a step to success!