I agree with Mark, it is hours of research. It took me a long time, but it has paid off. I emailed/phoned/skyped suppliers, I had narrowed down.
I also did internet searches to find out more about each company. Finally I put in small trial orders so that I was not loosing much if I had made a big mistake. Thankfully I haven't been ripped off, but I think that was because I read forum comments on Salehoo regularly, have been doing the training offered and researching the companies.
A long the way I ended up changing what I wanted to sell, but that has made it easier.
Yes, some websites are very difficult to navigate and with some you are unable to buy online, but do not let that discourage you if you see a product that you would like to sell. That's where numerous emails, phones and Skype conversations come in.
Now some of my suppliers are not ones I found on Salehoo, but after successfully using the tools and training Salehoo provided, I have been able to build up a small list if suppliers that I am happy to use.