Your passport must be valid until 3 months after your anticipated travel in Kenya. You must have a blank page for each country you will visit. Most visitors require visas with the exception of citizens of certain countries of the Commonwealth or otherwise. It is advisable to obtain visas in advance, from Embassies and High Commissions as several airlines insist on them prior to departure. They can also be obtained at the point of entry into Kenya.
The regulations vary depending on nationality and country of origin, and requirements may change, so you are advised to contact the appropriate Kenyan diplomatic or consular authority or tourist office before finalizing your travel arrangements.