The best and the safest way to sell your bitcoins is to be a part of trusted and reputed site and it will also depend on the country that you are living in as for me localbitcoins is the best place to sell my coins.
yes that is one of the most important point that you need to be very much careful about selling your bitcoin, you should really select a trusted means of selling your bitcoin.
Go to marketplaces in other forum and there are a lot of people or sites who are reputable which you can sell your bitcoins fairly. Avoid scammers who offers big money in exchange with your btc.. remember scammers will try to lure you first.