Do it slowly and sensibly and the results / health benefits will be better and longer lasting. I am real hater of "crash diets"
Plenty of water -YES
If your schedule allows eat 6 smaller meals a day
Reduced intake of fats
Vary your protein sources, Red meat/ turkey/ chicken and oily fish
The 5 a day cliché is a good guide, ensure 1 portion with each meal and a portion of carbohydrate (you still need them never cut them out)
Swap "white" foods for wholemeal (pasta, bread, rice etc)
Don't be afraid of a bit of flavour using spices and rubs rather than shop bought sauces
Regular exercise - 45 mins x 3-4 sessions per week minimum is plenty - over doing it wont make much difference as recovery is key
ALLOW TREATS - it keeps you sane and gives you something to aim for. When I am being strict I still have a Friday night off and have a few beers and a chippy tea, it is absolutely fine!!
Reduce caffeine even if you just knock down by one cup a day over the course a month that's 30 less caffeine drinks, it will make a difference
Supplements are not essential and I would never recommend to somebody who's medical background I didn't know. But some people will take various supplements and vitamins to support (but never replace) a balanced lifestyle.
Good luck and stick at it - the first few weeks of any type of change is the hardest part. Fatigue and feeling out of sorts is normal if you begin to withdraw and/or cut down on certain foods and stimulants - keep your water intake up it helps