good question---
I go by my gut feeling on a lot of my models. I like a challange, so some times I will get a simple kit to convert it into something more than it ever was intended for. Also I have a fondness for tuner type cars, so just about anything from this is an open door for me to build. And sometimes it just something that catches my eye and says hey this looks like it would be a cool model to build. I build more than just cars, so a tank, plane or boat model is right up my alley!!
Scott