Any tips

Seeing a picture of myself the other day was like a slap in the face and I finally have the motivation to lose weight.
I am going to be doing 30 minutes on a rowing machine 5 days a week to begin with and starting a healthy diet and I just want to use slimfast as a kick start for the first week.
I have a really sweet tooth and I'm worried that I wont be able to stick to it and will end up snacking.
Does anyone have any tips on how to stick to it and not give in to cravings?
I have just read through several posts with people saying they take multi vitamins whilst on slimfast. Is this recommended?
thanks :)