You should give notice of your intended marriage to the marriage registries either directly or through a civil celebrant of marriages before your wedding. There are no residential requirements for marriage and the marrying parties may be of any nationality. that is to say, you can get marryed in HK on a visit visa. Under the Laws of Hong Kong, you will have to go through the following procedures for solemnizing a marriage in Hong Kong:

Either one of you has to give a Notice of Intended Marriage (the notice) to the Registrar of Marriages (the Registrar) in the prescribed form either directly or through a civil celebrant of marriages.
The Registrar shall exhibit the notice in his office until the issue of a Certificate of Registrar of Marriages or the expiry of the 3-month period.
The Registrar may, at least 15 days after the giving of a notice, issue a Certificate of Registrar of Marriages to enable you to celebrate your marriage within three months from the date of notice giving if all the statutory requirements are met.
If the marriage does not take place within three months after the giving of the notice, the notice and all proceedings thereupon shall be void. You have to give another notice before getting married.