There are many ways to earn bitcoin.  Nowadays, there are many websites who needs services and offer bitcoin as payment.  You can try joining signature campaigns, advertisement promotion, referring commission, online jobs such as data encoding, captcha typing, and other professional fields depending on your capabilities and capacity. But remember to check the legitimacy and trust rating of the websites before offering your services.  When you already earn bitcoins, you can also try joining lottery that might double or triple you bitcoin in short period of time.  Those are some ideas on how you can earn bitcoin without investing.