How do I set up an affiliate marketing campaign?

I work for a media company that wants me to initiate an affliate network structure. At the moment I work in SEM but I have had no experience of affiliate marketing. I need to know the very basics about where and how to start building this from scratch. And, does anyone know what sort of timescale I would be looking at for initial implimentation? It will be focused on the finance industry. Particularly B2B.