Chinois are essentially strainers that are best for very finely reducing the amount of solid material in home-made sauces, like traditional Italian Red Sauce. Different from any standard strainer, chinois strainers aren’t really to be used for standard things like straining pasta, although they certainly can be.
What you’re looking for in a good chinois is pretty simple, and the most important thing is that it’s made out of stainless or another type of steel that will last a while. They can get bent, especially if you don’t store them in the right place, and having a chinois that is bent can certainly negatively impact its straining capability.
Look for a good brand, something like a Cuisinart or New Star, something by a company that you know makes a quality product. I recommend having a couple different chinois, perhaps 2 to 3 at varying sizes, just to help you in a pinch in the kitchen if you have multiple dishes going on.
