I guess it depends what you mean by reliable. I would be asking two main questions....

Are they reputable? (The last thing you want is for them to run off with your money) Check their registrations, insurances etc.

What returns do they forecast and what is their historic performance? Although, obviously, past performance is no guarantee of future returns. I did see on one site that Ken Fisher thought in 2007 that the market was due a minor correction...

Anyone (almost) can make money in a bull market, the key would be to see how their perfomance rated against the market over the last 18 months.