This might be a tricky task for many. However, it's not so hard. Here are a few tips for finding trusted crypto casino:
1. Check reviews online. Just enter the casino name to Google and add "review". For ex.: Cryptocasino Review.
You will find a lot of details. Check some and read real reviews left by customers.
2. Avoid unlicensed casinos. If the casino hasn't one, it can just take your money and never pay your winnings.
3. Find out if casino uses SSL. It must use https. Not http://. If it doesn't have SSL, don't use it.
4. Do not use casino if your country is banned - you will never get your winnings if casino asks to confirm your identity.

I hope these few tips will help you. I found out this the hard way. Won some Bitcoin on shady casinos and never got my winnings. They just banned my account.