If it's a standard product, then just pick a few suppliers from Alibaba and ask for samples. You should find that for standard products, the vendors have mostly the same type of products at mostly the same prices.
If it's any sort of custom product, I'd start with a sourcing company like Global Sources, Berkeley Sourcing Group, or Radius Product Development.
You could go directly to the manufacturer, but if you've never done that before, you are likely to end up extremely frustrated. The problem is that the manufacturers in China tend to do exactly what you tell them to do, and if you've never done manufacturing, you are likely to tell them the wrong thing. You also have the problem that there are high quality, reputable factories (most of them), but there are also scams and rip-offs, and as a newbie, you are likely to fall prey to problems.
The companies that I mentioned provide a frontend to the Chinese manufacturing system.