Seed buying is a trust game. The buyer needs to feel, that to the best of the sellers ability, that the seeds they buy are what is advertised.
All I can say is time will tell. I am certain that if somebody out there is selling "faulty" seeds, that the word will get out there soon enough. A reputation can be destroyed in an instant these days.
Here are some tips:
1. Ask around. "Rich", to me, is first class in every way. I have bought seeds from him, and they bloomed like I thought they should. "JWWC", just ask around here...and we all know that he is a very ill person who buys too many plants. I am sure that other names can be presented here. There are many good sellers.
2. When I got started, in 2002, I made it a point of using my own images. I wanted folks to know that I owned the plants. Mine are more a mix these days, but certainly the more the seller is using his own pictures, the higher the comfort level you should have..
3. Start small, from a variety of sellers. Then, as your comfort level grows, focus on the plants and the sellers you trust. I have some buyers who have been with me the entire time.
4. Do your research. I occasionally see crosses that make my head shake. Pod parents listed that have never ever produced seeds. If a cross is just too good to be true, it just might be.
Hope this helps,
Steve