To enter Kenya, you must have a passport with at least six months validity at the time of visa application.
You must also be in possession of a return air ticket.
On entry into the country, a stamp is placed in the passport showing the length of stay.
Tourists are advised to declare the actual period of stay in Kenya and to check the stamp in their passport; extension of stay can only be obtained from the relevant immigration offices.
Penalties for failure to comply with this procedure can go as far as arrest.
To enter Kenya, the passport must have at least one full blank page in order to affix the entry visa. If this is not the case, travellers may not be accepted into the country and may be flown back to Italy on the next available flight.
For any changes to the required residual validity of your passport, it is advisable to check in advance with the country's embassy or consulate in Italy or with your travel agent. 
It is compulsory to obtain a paid entry visa to enter the country.
The visa categories are as follows 
1. Transit visa (USD 20) with a maximum validity of 72 hours.
Visa application also available at http://evisa.go.ke/evisa.html 
2. Tourist visa (50 USD or 40 EURO) valid for one month, three months and renewable up to six months; visa application also available at http://evisa.go.ke/evisa.html 
3. Multiple visa (multiple visa, 90 EURO) for business. Valid from one month to one year. The application must be submitted to the Kenyan Embassy in Rome. Among the documents required, the letter of invitation from the local company must be presented.
4. single journey visa (51 USD)  
5. East African Tourist Visa: valid for 90 days (Multiple entry visa USD 100), allows travel to Kenya, Rwanda and Uganda. You apply in the first country of arrival. If in Kenya, it is obtained from the Kenyan Embassy, if in Uganda it is applied for at the respective Embassy, if in Rwanda it is obtained online on Rwanda "evisa". 
The Kenyan authorities have announced the introduction of an online procedure for obtaining an eVisa.
It is advisable to follow this procedure, which can be accessed at the following address: http://evisa.go.ke/evisa.html (in English only).
The Kenyan authorities have indicated that it will still be possible to apply for a visa at the accredited Kenyan Embassies in the country of residence and at the airport. In this regard, attention is drawn to the fact that the Kenyan Authorities accept payment of the relevant fees in newly issued US dollars.
Payment can also be made in the equivalent amount in Euros.
For further information, it is advisable to contact the Kenyan Embassy in Rome, which is responsible for issuing entry visas. 
Currency and customs formalities: tourists can freely import foreign currency up to a maximum of US$ 10,000 with a special declaration. Beyond this limit it is necessary to fill in a form for the Central Bank to be handed in when entering or leaving the country.
It is advisable to change currency only at authorised offices (banks, hotels and exchange offices). 

(source: Viaggiare Sicuri, Italian Ministry of Foreign Affairs website)