I’m just getting into surface mount PCB design. I’ve only done one board for a class project, and the components supplied were all through hole. So before I get started on my first surface mount design, I’d like to understand the basics on this subject. 

Q: How can I choose the correct package size for surface mount passive components? In other words, what factors drive the decision to use an 0603 SMD resistor/capacitor and opposed to using a 1608 package? 

If anyone can provide information on this subject, I would greatly appreciate it.

Thank you in advance =)