I think my original question got lost in the sauce there. I'm trying to gather resources for advanced and specialized harvesters but I'm having difficulty finding the ingredients. Is there any rhyme or reason to what planets spawn what materials or is it just a question of exploring and surveying everything until I find what I need?
According to SirEmi himself (http://forum.astro-galaxy.com/index.php/topic,8370.0.html):
small planets / moons have a higher probability to contain rare resources, so scan those first then deciding where to start mining a star ...