HK Visa requirements for Bangladeshi

Hi! I have a valid visa for China till 14th November 2012. I want to get HK visa for transite purpose and tour as well. I am an employee of a large company in Bangladesh doing Mobile Phone importation from China and I need to travel to China every one or two months as when as required by my Company for meeting with suppliers.
Now, for easy travel to Shenzhen and also to travel to HK as tourist I would want to get HK Visa.
Please help me with the proper requirements for me to apply for HK Visa.