There are currently so many binary options brokers that it's becoming really difficult to keep track. Some of these brokers are huge giant financial entities, while others are nothing more than mom and pop shops, 1 man shows that try to build nice looking websites with the hope of enticing unsuspecting visitors into depositing their money with them. These scammy websites will then do everything within their power to prevent you from winning bids. This can happen by altering stock quotes, altering expiration times, and if all else fails and you still manage to win some money, they'll just simply not let you withdraw your funds.
Obviously, you should steer clear of these brokers. The best way to do this is use the internet for what it's best for - information gathering.
The internet is full of binary options broker reviews, like this Anyoption review for example. These reviews are usually made by people who have traded with the broker in questions and have had some experience which they wish to share with the world. This is critical and will definitely help you get a better idea if where you'd like to do your binary options trading.
Put some time into it and make your decision. Binary options trading can be very rewarding, but if you register at the wrong broker, you can also end up losing your entire investment. Be careful and do your research. That way you will exponentially increase your chances of really making money instead of losing it.