You will know when a site is trying to scam you if it doesn't replies to your queries. Like for example if you have encounter in making a deposit or requesting a withdrawal, of course you will contact their support to solve the problem, if they do nothing within 1-2 days then probably it is a scam.
Sometimes yes, but most of the time, they have a sweet tongue. They talk very nice and even assist you in depositing. Aside from the sites security, what I always look at when I am about to deposit in a site is the reviews in the internet. No review, I won't deposit, Negative reviews, well that's a sign that it's not worth it to deposit and do a business with such site.