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: see which authority is listed in the footer, because some sites quietly block certain regions. After that I look at banking: card, e-wallets and bank transfer should all be there, and there should be no weird fees on cashouts.
Never judge a site by the bonus alone. Wagering of 35x or 40x is normal, and some games count less towards it. A good recent review that covers all of this can be found here [url=https://admin.phacility.com/F644074]oficjalna strona[/url] and it saved me some time.
On mobile I mostly use the browser version, and if there is an app I make sure it comes from the official page. Support matters too: a real human reply beats a bot loop.
Anyway, that is my routine. Set a budget and stick to it.