Best source and most profitable to me is getting a job which pays you in bitcoin. Many on this forum pays bitcoin for those who can work Computer based freelance. Its better to work on your skills and develop them.
Indeed, this is the best way of making bitcoin by looking for jobs which are ready to pay you in bitcoin. There are now many companies in market which are not only accepting payments in bitcoin but also paying in bitcoin. This practice is not only good for bitcoin survival but also for public. Bitcoin is ever green investment. Besides this, you may earn it through famous signature campaigns, mining and trading.