Valid passports or internationally recognized travel documents valid for at least 6 months are required for entering Malaysia. Remember that Sabah and Sarawak are treated like separate countries, and you will have to go through customs again there, both from Peninsular Malaysia and between the two states.
A social single-entry visa valid for 3 months can be applied for at Malaysian diplomatic missions overseas. Check www.tourism.gov.my for details about formalities and visa requirements. Citizens of most Commonwealth countries, Ireland, Switzerland, Netherlands, San Marino, and Liechtenstein do not need a visa to visit.
The following countries do not need a visa for a visit not exceeding 3 months: Austria, Italy, Japan, South Korea, Tunisia, United States, Germany, France, Norway, Sweden, Denmark, Belgium, Finland, Luxembourg and Iceland. You are not allowed to be employed with this visa.
Extensions may be applied for at any Immigration Office.