A trader can evaluate a broker to guarantee that whether all the claims made by the broker are actually reliable and obtainable or not before he can make investment in that broker. And yes to judge the effcieincy of the services provided by a broker a trader can use demo account of that broker. However a trader should not greed for bonus offers as today traders are receiving bonus offers from their platforms and many innocent beginners fall in the trap of fraud brokers in the dream of earning bonus offers only.
A trader should try to work with a broker who can ensure him tailor-made services so that his live trading passage with the real capital can be safe and easier.