I originally started on a Wednesday, but changed my WI day to a Friday, because Friday was normally the night I ate a few more bits than I should - gave me a whole week to fix it. Best tip is fill your cupboards with healthy bits, get rid of junk if you don't think you can handle it, because at least that way if you want to snack or you mess up and have a blow out, you've done damage limitation - it's much harder to go down the shops than it is to grab something quick out of a cupboard or fridge!
Plan ahead, try and plan a rough weekly guide for dinners etc, so you know what you're having and what wiggle room you can give yourself for Syns/Treats - even if you don't do it 100% and fancy something different, you'll probably subconsciously pick stuff fairly similar.
Most importantly, don't be too hard on yourself, if you have an off day or an off meal or feel rubbish, you are not alone, jump back on it but don't beat yourself up, it's a vicious cycle if you let it get you down - the more down you are the more you'll want to eat.
Good luck!
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