To apply for a HK visa, the following documents are required:
(1)Photocopy of the applicant's travel document containing personal particulars, date of issue, date of expiry and/or details of any re-entry visa held (if applicable)

(2)Photocopy of proof of the applicant's financial standing, e.g. bank statements, savings accounts passbooks, tax receipts, etc. and proof of employment (if any), e.g. company leave letter, salary slips, etc.

(3)Photocopy of proof of transportation arrangement, e.g. flight itinerary

(4)Photocopy of proof of the proposed leisure visit to Hong Kong

For more info, read this page:
http://www.immd.gov.hk/ehtml/id1004.htm#VI