Wifi Keeps Disconnecting

My iphone 5 keeps failing to recognise my wifi at home. It never automatically connects when I come home, and it oftens disconnects if I stop using my iphone after a short period of time (locked and unlocked).

Are there any settings I need to adjust? Or do I need to take my phone into the shop?

My phone is a week old, so I imagine I have the newest operating system?

Thanks,

Jonny