Gambling is not just about winning or losing, but how do you keep your mentality stable too, even if you win big but if you can't withdraw your money from the gambling site then it's pointless, i'm sure the majority of people who get stuck in withdrawal problems on a gambling site because they didn't read the TOS first are beginners, usually they are lazy;
1. find out the reputation of the online gambling site
2. check the reviews and legitimacy of the gambling site
3. check the age of the gambling site
4. ask other members whether the bonuses offered are legit
5. read the Term of Service
Though age also matters, I believe reputation shouldn't be based on the age of a platform. There might be a platform that was launched last month or a couple of months ago but has been operating very well and its customers might have no complaints regarding anything, this also makes the platform reputable, and an old platform might decide to start acting weirdly all of a sudden and stop paying users what they owe them and might even shut down their services without any notice, this happened recently with a casino on this forum I won't take the name.
But, it is true that a platform that continues to provide the best of its services for quite some time deserves to be trusted because it has been around for quite some time and users were always served right by the platform. So, users should basically look for user satisfaction regarding a platform to evaluate its reputation and trustworthiness.