The rules of diplomacy apply: Trust but verify. You can trust whomever you like, but if the charts don't verify then you may as well get down on your knees and pray.
For me to trust someone, they would have to: a) make a lot of money trading, and b) not make much money telling other people how to trade A successful trader who has written a book might fill this bill, but only if it isn't a book that's a thinly disguised advertisement for their other services. You don't usually make much money from writing a trading book. In other words, if they also had some fancy web site inviting me to join for a high fee, I would not trust them. This is not to say there is nobody out there charging hundreds a month who is not legitimate and successful. Probably some of them are. But there is no way of sorting that out. Contrary to what some people write on ET, I think there are those who want to share their knowledge. In addition, when I do read anyone's book, I look for them to discuss how to avoid losing money. I think this is actually more important than making money.