Start off doing 2 to 3 days a week with tuesday and thursday as a rest day. This will help you get used to the regular exercise. Alliteratively ride in on monday, take other means home on monday and back on on tuesday, ride home tuesday etc..
Leave as many clothes at work, for example I leave my suit and shoes at work, this means all I need to take to work each day is a shirt, socks and pants. Some people leave their shirts at work and get them dry cleaned.
Roll your shirts in your bag, it helps prevent creases.
full length mudguards are pretty useful, keeps most of the water from the road off you and the bike. As such meaning you need to clean your bike less and your bum won't get as wet.
Eating will depend on you. Things like bananas and pasta are obviously good to eat.