There are variable methods to earn BTC, depending on multiple factors the most important of which is whether you already have BTC and ready to invest it, as well as having specific skills like coding or designing:

*Trading bitcoins for USD equivalent and vice-versa and buying and holding cryptos, a high risk investment.
* HYIP, matrix, multi-level marketing, and anything along that side, which are scams
* Doing freelancing for BTC, the chances increase with having skills
* Faucets and free giveaway, easiest but least paying.