Not always easy to tell, but there are things to look for. A generalisation: if the casino uses Microgaming or Cryptologic (Wagerlogic) software, you can be pretty sure the software vendor is pretty stringent on who gets their licences. If you go with a Playtech, or IGT casino then you’ll usually be in safe hands, whereas with the other vendors it’s a bit hit and miss – good and bad exist out there!
A number of casinos display various “seals” of legitimacy from independent regulators, along with audited payout certifications. While none of these guarantee safety, seals from eCOGRA and auditing by PriceWaterhouseCoopers are generally signs that the casino is at least working with people with the right intentions.
One of the things I always look for is the “about us” page. I expect to see information here that reinforces the casino’s operations and gives me confidence. Transparency of information is not a good thing, but if they are licenced in Gibraltar, Australia, the Isle Of Man, Malta or Alderney, these are strict jurisdictions who care about how the business world views them. You’ll be able to add the UK to that list in the coming months I expect as new laws are introduced. Here’s my own perception of the strictness of jurisdictions that regulate online gambling companies: Alderney (strict), Australia (strict), Antigua & Barbuda (not very strict), Costa Rica (not very strict), Curacao N.V (not very strict), First Cagayan Philippines (not very strict), Gibraltar (strict), Isle Of Man (strict), Kahnawake (reasonably strict), Malta (strict), Vanuatu (reasonably strict). There are one or two other minor jurisdictions but not ones I know much about to be honest. More on this in the Licencing and Regulations section.
Obviously the best recommendations come from other players, and there is little better than to search the forums at Casinomeister to get an indication of how a casino is performing. As a general rule, the less threads in the “complaints” section the better, although the vast majority of complaints are bonus related and do not necessarily reflect on the operational aspects of a casino. You have to bear in mind that casinos don’t generally like players trying to profit from “free money” without taking a risk of their own, which is why bonus terms get convoluted and cause so many disputes.