To know the correct date, you can either use a vaisnava calendar application, or consult with the local ISKCON temple (or get a calendar from them), or by use the internet: the information is easily accessible.
After rising early and taking bath (preferably applying tilaka as well), it is advised to come before the Deities, or a picture of Sri Krishna, or just think of Sri Krishna and state what vow you will follow until the completion of the fast and request Sri Krishna for blessings and the power to do so.
The Ekadasi vrata ends the next day. At that time, you can take a piece of grain or a glass of water (if it was nirjala/no water fast) and by stating to Sri Krishna that now you will complete the fast, you consume the grain or water. With this, the fast is successfully completed. But be careful with the timings! The ‘parana time’ (time for completing the fast) is usually not longer than one to two hours, so it is better to check the calendar.
