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.
First thing is the licence: check who regulates the site, and whether they actually accept players from your country. Then payments: I want at least one fast e-wallet option, and cashout times should be listed up front.
Never judge a site by the bonus alone. Anything above 40x rollover is a red flag for me, and the bonus usually expires in a week or two. A useful overview with bonus rules, app info and payment methods is here official site so you know what you are signing up for.
On mobile I mostly use the browser version, and if there is an app I make sure it comes from the official page. Test the live chat before depositing: slow or scripted answers usually mean trouble later.
Hope this helps someone. Only play with money you can afford to lose.