you must be at least 18 years old
you must have legal capacity
you must not already be married or be in a registered partnership
If you are not Swiss, you must have the correct entry visa for your country of origin in order to stay in Switzerland legally until you are married
A double surname (both the wife and the husband's surname, such as "Rossi Bernasconi") is not permitted.
However, adding a hyphen between the surname of the wife and that of the husband (e.g. Rossi-Bernasconi) makes a difference: the surname is permitted, but may not be entered in the civil status register. You can use your hyphenated double surname in your everyday life and, if you request it, it can even be entered on your passport and other identity documents.
However, it makes you eligible for the simplified naturalisation procedure.
Preparations
Ask the civil register office at the place where you want to get married which documents you need to bring from Switzerland.
Inform the Swiss embassy/consulate in the foreign country concerned that you intend to get married there.
Ask the authority responsible for migration in your canton of residence or the Swiss embassy or consulate abroad about the conditions of entry and residence in Switzerland that will apply to your future spouse if they are not Swiss and do not already live in Switzerland.