How should the names of species be written scientificaly?

Species names should be written in italics, with the genus name capitalized and the species name in lowercase. For example, Homo sapiens is the scientific name for humans. When writing, the full name should be used on the first mention, and subsequent mentions can use just the genus initial (e.g., H.). Additionally, if the species name is referenced in a non-italic format, it should be underlined.