Literally, bitcoin is money. Therefore you can get bitcoins in the same way you earn money. Any work or job is useful to earn some dollars that you can change for bitcoins later.
That's the point. Any ways that earn money can be the ones to earn bitcoins.
But in the earning of bitcoin we have to keep in mind that nowadays we cannot earn bitcoin in offline work/job but we can earn only on internet and in the activities which can be done on internet. On some places shops are also earning bitcoin.