Long time lurker here, so here is my short checklist for choosing a casino site. After trying maybe a dozen sites I learned to read the small print first.
First thing is the licence: find the licence number and look it up, because some sites quietly block certain regions. Next come deposits and withdrawals: card, e-wallets and bank transfer should all be there, 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 good recent review that covers all of this can be found here <a>lottoland uk</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. Treat it as entertainment, not income.