Long time lurker here, thought I would drop what I look at before signing up anywhere. After getting burned once or twice I stopped trusting the big banners.
First thing is the licence: see which authority is listed in the footer, because some sites quietly block certain regions. After that I look at banking: I want at least one fast e-wallet option, and there should be no weird fees on cashouts.
Bonuses are the tricky part. Anything above 40x rollover is a red flag for me, and some games count less towards it. A decent independent write-up with the current terms is worth a read here [url=https://www.intensedebate.com/people/id1tqheaim]casino trino[/url] and it saved me some time.
Most of my sessions are on mobile, so I check how the lobby works on a small screen. Ask support one simple question first: if they answer in a couple of minutes that is a good sign.
That is about it. Only play with money you can afford to lose.