The first thing you need is information - whether you are a small, large, or medium sized organisation, and no matter which sector you work in, you need to learn about how and why people commute in the way they do. Using this information you can start to understand what might encourage the non-cyclist or infrequent cyclist to use their bike more for work purposes. You can do this through a travel survey (ways2work).
This information will help you to understand the level of cycling in your organisation and the reasons why. It may be that your offices are located near busy roads which deter cyclists - so you may have to deal with that issue before anything else - or it may be something much simpler such as lack of drying room facilities.
It is important to make the cyclist and prospective cyclists feel valued and supported. This comes in many forms from the hugely important issues of cycle safety and training.