You can visit government website www.info.gov.hk or www.esd.gov.hk which have all HK government department's information and contact details. Also, you can obtain information via the following websites.

Invest Hong Kong – Application for work permits
Website: www.investhk.gov.hk, Tel: 3107 1000, Email: enq@InvestHK.gov.hk  

The Immigration Department – with Visa & Hong Kong Identity Card enquiries and application
Website: www.immd.gov.hk, Tel: 2824 6111, Email: enquiry@immd.gov.hk  

The Inland Revenue Department – for tax matters
Website: www.ird.gov.hk, Tel: 187 8088, Email: taxinfo@ird.gov.hk  

The Transport Department – responsible for driving licenses & car registration
Website: www.td.gov.hk, Tel: 1823/ 2804 2600, Email: tdenq@td.gov.hk  

The Labour Department – for work contracts for domestic helpers
Website: www.labour.gov.hk, Tel: 2717 1771, Email: enquiry@labour.gov.hk