Practical information
Local currency
Ukrainian hryvnia is the only currency you can use legally in Ukraine. The current rate is about 10 UAH/€. You can exchange the money at the airport, however, the rates are not best there. So you are advised to change only a small sum at the airport for transportation (50 € are more than enough); in the city center you will be able to change at a much better rate (there are lots of exchange offices all around the city).
Language
Most Kiev citizens speak Ukrainian and Russian. Thanks to the EURO-2012, you will find some information in English on the streets, although not so much. Fortunately, a lot of people (especially young) speak English besides Russian and Ukrainian, they will gladly help you if you need.
Time
Ukrainian time is GMT +3 or CET (Central European Time) +1.