There are several ways to obtain bitcoin. the easiest way is to mine it using mining equipment, but you need some money.
the other way is to trade it. Buy when low, sell higher and repeat this to obtain more coins.
Mining is not really the easiest way to earn Bitcoin. There are a lot of faucets in the internet and you just need to choose one of them, well it is not the most suggested way of earning them but we are talking about the easiest way which is faucet. In terms of people earning Bitcoin in these forum, Signature Campaigns are the most popular.