Easiest and cheapest are going to be two different things, I know you only mentioned easiest so I'll just go forward and say the easiest would have to be using an online marketplace such as Paxful and Localbitcoins, though they do incur pretty hefty fees but it matters on what way you want your money back. (Example - cheaper to have money go straight to cash to your bank account)
Cheapest would have to be using a service such as Coinbase, Kraken, BTC-E and so on which allows you to sell and buy bitcoin but you usually must adhere to KYC laws which will take some time to verify all of your ID, Passport and so on.
An exchange or Bitcoin ATM is probably the easiest method to convert bitcoin to fiat. Although most exchanges will require a certain amount of personal information in exchange for this ability.
Those may be easy, but those Bitcoin ATM's take a disgusting amount of money from you. Just steer clear from them unless you're really that desperate to sell quickly. Plus I highly doubt your area has one close to where you live, I know I don't.