At the end of your tenancy you are able to either give the correct notice period that you contract states and move out at the end of your tenancy term or request a tenancy extension.
When you depart it is worth returning to your inventory and making sure the property is returned to the landlord in the condition that it was made available to you, this should avoid any disputes and make it easier to get your deposit back without undue delay.
Before you depart:
Thoroughly clean the property including carpets, windows, furniture walls and woodwork.
Allocate time to making sure the garden is also left neat and tidy as this is a common area that gets neglected before departure.
Clear away any of your own possessions and remove everything from the property that belongs to you and was not there on arrival.
Return all keys to the landlord.