Make sure there's an inventory and take plenty of photos of the house at the start of your tenancy – this shows what was there when you moved in and if anything was already dirty or broken so your landlord can’t blame you later and try to keep your deposit.
You can make your own inventory if the landlord doesn't arrange one. Try to get the landlord to sign it along with everyone who lives in the house - if the landlord refuses to sign, get an independent witness to sign instead.
Shelter has more information about inventories and a useful inventory template to help you make your own.
Make sure you tell the landlord in writing if there is any disrepair in the house so you won't be blamed for it later.
When you move out take more photos and keep proof of payment for any goods or services you used to show you left the house in a good, clean condition.