Getting a good-natured legendary, non-uber?

Pokemon like Heatran, Azelf, and Zapdos are seen in the over-used category. However, they must be good natured. How do you control this? Do you just save before catching it and hope for a good nature? Or, does the Abra-synchronize technique work? Please help, and thanks! Also, is there a way to get a Heatran in HGSS?