Mostly a reader, rarely post, thought I would drop what I look at before signing up anywhere. After trying maybe a dozen sites I stopped going by ads alone.
First thing is the licence: check who regulates the site, because some sites quietly block certain regions. Then payments: card, e-wallets and bank transfer should all be there, and the withdrawal limits need to be written clearly.
Never judge a site by the bonus alone. Read the wagering and the max bet rule, 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/idl5hzu3te]Wildrobin[/url] so you know what you are signing up for.
On mobile I mostly use the browser version, and a good site loads fast and does not log you out every five minutes. Ask support one simple question first: slow or scripted answers usually mean trouble later.
That is about it. Set a budget and stick to it.