Welcome, Eric. Which company?
There's no fixed set of criteria that works universally for all custom projects. There's questions about theme, target audience, budget, etc. I do this kind of consulting as a sideline. My biggest clients are Uusi and Gambler's Warehouse. You should get in touch with me via email or private messaging here on the forum.
I will say this much - it's best to get a quality printer. Most printers, quality or otherwise, with rare exception, have their manufacturing done in Asia. The largest exception is the United States Playing Card Company, of course. The wrong printer can result in a world of headaches. I recall one project that went through hell with its printers - after FIVE printings, still flawed. Everyone attached to that project lost money, big time.