To shiny hunt starters in Heartgold, you will need to firstly obtain a starter Pokémon from Professor Elm. You can then start your hunt by using the PokéRadar method or chain fishing. The PokéRadar is the more reliable method, but it can take some time and effort to get it to work properly. Chain fishing is less reliable but much faster. Whichever method you choose, keep at it and eventually you should find your shiny starter!