Long time lurker here, thought I would drop what I look at before signing up anywhere. After trying maybe a dozen sites I learned to read the small print first.
Licence comes first for me: check who regulates the site, and whether they actually accept players from your country. Then payments: crypto is a plus but not a must, and the withdrawal limits need to be written clearly.
The welcome offer is where most people get caught. Wagering of 35x or 40x is normal, and some games count less towards it. A good recent review that covers all of this is here <a>Gamba Casino app</a> so you know what you are signing up for.
Most of my sessions are on mobile, and if there is an app I make sure it comes from the official page. Ask support one simple question first: if they answer in a couple of minutes that is a good sign.
That is about it. Set a budget and stick to it.