You have a choice of whether to cycle to work in your work clothes or carry them with you and change when you arrive. Obviously which you do depends on whether you have a long, strenuous journey or your workplace is just a short, flat couple of miles away.
If you have access to showers or washing facilities keep a towel at work and change when you arrive. Some workplaces have power showers and changing rooms, others will just have a sink. If you haven't got time for a shower, at least have a wipe down with a flannel or babywipe and add a squirt of deodorant, for the sake of your colleagues!
What to wear
Choose clothes that won't look crumpled if they've been squashed in your panniers or backpack. Modern fabrics mean that ironing and pressing isn't always necessary and many offices are adopting a more casual look, in any case.
Carry a spray bottle of water that you can squirt your clothes and hang them up while you take a shower - and even a suit will be nice and smooth.
Some people drive or take a train in on Mondays with a week's fresh laundry and then ride the rest of the week, others bring a change of clothing in every day.
Roll rather than fold clothing, you will get fewer creases that way. You can also use specialist shirt carriers such as the Eagle Creek. Other ideas include putting the clothes in a carrier bag and stashing at the top of your pannier or backpack.
Some people advocate riding with a breathable layer underneath a shirt then changing on arrival.
Then there are the advocates of 'Slow Cycling' who think that riding to work is not a race so you shouldn't arrive sweaty anyway therefore saving time on having a shower. But check with your colleagues first before committing to this one, as no one wants to sit next to someone who is sweaty and smelly!