Lard is used in cooking and pastry making for its wonderful flavor. However, what you substitute for it depends on what you are using it in. In pie and pastry making, for example, you can substitute any other hard fat like Crisco (which is a hard vegetable shortening) or butter. And substitute it in equal measure. In cooking, however, any fat will do, from butter to olive to vegetable oil. The only thing you need to think about is the taste. So if you are not sure what the lard brings to the dish in terms of flavor, then substitute vegetable oil, again in equal measure.