Find a job (part time or full time) that pays in Bitcoin
Start a business and have Bitcoin as the major payment system.
Do freelancing works that pays in Bitcoin
Offer whatever skills you have and accept Bitcoin as payment
You can mine for Bitcoin
Last but not the least,
You can also buy Bitcoin in exchange of fiat.
Consider Bitcoin as the fiat money you have. How do you Increase (earn) fiat?
It's the same for Bitcoin.
Actually, this forum helps me a lot in terms of increasing of my bitcoin. Right now I participate in cryptotalk campaign where they pay me in every that I have made. This forum has a lot of sections that will help you to increase your bitcoin. You can also check the services section because most of the work there is bitcoin payment. Working hard will be the key to help you to earn and increase your bitcoin. But, you can increase your bitcoin just exploring this forum.