Been reading this board for a while, so here is what I look at before signing up anywhere. After getting burned once or twice I learned to read the small print first.
Licence comes first for me: 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 cashout times should be listed up front.
The welcome offer is where most people get caught. Read the wagering and the max bet rule, and some games count less towards it. A useful overview with bonus rules, app info and payment methods is worth a read here [url=https://pbase.com/solkrypto43b1c0/smashcasinorealmoneygami19daea]Smash Casino bonus[/url] so you know what you are signing up for.
On mobile I mostly use the browser version, so I check how the lobby works on a small screen. Support matters too: if they answer in a couple of minutes that is a good sign.
Hope this helps someone. Set a budget and stick to it.