The majority of Bitcoin Casinos also accept traditional payment methods such as Credit Cards. In that respect, they have to be licenced and regulated by a reputable gambling authority, in order to operate in specific jurisdictions.
Although a casino needs to prove to be fair, it is also necessary that you check that the casino is licenced. This is only a small step in confirming that a casino is trustworthy. You can usually check this in the footer of the website. Most casinos have a link to their licencing certificate there.
That being said, it is also essential to check that the casino is regulating by a prominent gambling body. A Bitcoin Casino that is regulated by the UK Gambling Commission, the Malta Gaming Authority or the Curacao e-Gaming is some of the best examples.
The licences and regulation are in place to ensure that a casino is not cheating players from their money.