While waiting for the official 12wbt to start it's recommended you start with making two small changes.
They should be something that's easy to 'win'. We're talking baby steps here.
So here's my two changes -
* Drink a 600ml bottle of water a day. More often then not I don't really think about drinking during the day. I have a cup of tea in the morning and maybe another one or a coffee around lunch time. Then around 8pm I start to get really thirsty and have 2 or 3 glasses of water just before I got to bed and that's never a good idea I'm up and down like a yoyo at night.
* Mini training sessions at work. Between 9 and 11 I'm usually sitting at my computer or reading a book with the occasional customer, great time for a bit of a workout. I wont be able to do cardio (sweaty is not a good look working in a cafe) but I can do strength exercises like curls (milk bottles make great weights), squats, lunges and bench push-ups.