It is always worthwhile taking these things easy, especially if it's your first detox. Ideally you want to detox over a weekend when you have few plans in the diary; rushing about on an empty stomach is just asking for trouble.
I would advise a 2-3 day juice detox, which will really flush out those toxins. I tried Nosh Detox (a service that delivers pre-blended juices to your door) last January and had great success - weight loss, clearer skin and bags of energy, plus the results lasted a good six weeks after I’d finished which was impressive. The great thing about this detox is that you get a planner that fills up your whole day with things to do, from drinking water and juices to having a salt bath and body brushing. Not only does it leave you less time to think about food, it also ensures that you drink nutrient-rich juices along with plenty of herbal tea and water so you won't feel famished, light-headed or like you want to give up.
If you want to do the detox yourself without delivery, I'd recommend starting the day with a hot water and lemon to help flush out your system, then blend up any fruits or vegetables you fancy. Make sure to use a blender rather than a juicer as most of the nutrients are in the skin of fruit and veg, so you want to keep that in your drink. If you get hungry have salad, vegetables, fish or chicken - it's far better to give in to healthy foods than keep going until you end up gorging on a pizza!
You can also boost the effects of your detox by dry body brushing in the morning with Neal Yard's Detox Toning Oil, £13.70, and having a bath at night with the addition of a handful of Dead Sea Salt, £6.99 (from Boots), and an essential oil of your choice (most have therapeutic qualities, juniper berry and grapefruit essential oils are good for detox) to make it smell pretty.
My final tip; try and rope in someone to give it a go with you. That way you can encourage each other not to give up.