Long time lurker here, thought I would drop what I look at before signing up anywhere. After a few bad experiences I stopped trusting the big banners.
Licence comes first for me: see which authority is listed in the footer, and whether they actually accept players from your country. 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 the bonus usually expires in a week or two. A useful overview with bonus rules, app info and payment methods can be found here [url=https://tdmromania.ro/member.php?action=profile&uid=21940]Rolletto[/url] so you know what you are signing up for.
I play almost only on my phone, and a good site loads fast and does not log you out every five minutes. Ask support one simple question first: if they answer in a couple of minutes that is a good sign.
Anyway, that is my routine. Set a budget and stick to it.