There are several ways to earn bitcoin. You should find the best one for you, but do not limit yourself to that one way.
This is the one that everyone thinks of first. Buy a computer or parts and run the program that mines bitcoin. The thing is that the specialized computers (ASIC) are expensive and they use a lot of electricity to do their work. When you do your math, you will probably find out that you are mining at a loss. Though mining at a loss could be done to help protect the network and your existing balances.
Another idea is to mine a bitcoin clone which is called an alt-coin and then sell them on the open market for bitcoin. Which leads us to trading.
Do work for bitcoin
You can work for someone who pays bitcoin, or work for fiat like US dollars and buy a little bitcoin every week from an exchange like coinbase that is in your area. Coin worker is a website where you complete tasks for points and trade the points for bitcoin and withdraw to your own wallet.
Sell something online for bitcoin
Purse is a website that host sellers items on sale for bitcoin in addition to allowing people to buy items from other people’s amazon wish lists for bitcoin.
Sign up for bitcoin faucets
A bitcoin faucet is a website that gives out small fractions of a bitcoin in a time based manner as a drip. I like to use Freebitco.in. You earn a fraction of bitcoin every hour that you can click the button on the website. You also get 4.08% APR on your balance on the site credited daily and you get a commission on all of your referal through a link that they supply you with after you sign up.
The point to trading is to buy low and sell high. You can trade different pairs. You can trade US dollars versus bitcoin or specific alt-coins versus bitcoin. If you don’t know how, you need to sign up to an exchange and look at the data for each market. Coinigy is a great charting website that links to the exchange so you can perform your trades right next to the chart.