Topology??

Hi Katy aartygecko ,

https://cgcookie.com/courses/blender-mesh-modeling-bootcamp

is an absolute must. Then there is also this:

https://cgcookie.com/courses/introduction-to-retopology

The rest is experience. There are no absolute rules that you can blindly follow. Every new model is a Topology puzzle that you have to solve. It can be both exiting and/or frustrating, depending a lot on your mind-set. But what I am trying to say, is that you don't learn all about topology in a few days...your knowledge will grow over time like a beautiful plant, that will stay with you your whole life (if you keep nourishing it), growing larger and larger...

As an extra I'd also throw two old but filled with timeless knowledge courses:

The Post Apocalyptic vehicle:

https://cgcookie.com/courses/modeling-a-post-apocalyptic-vehicle

The Sci-fi Helmet:

https://cgcookie.com/courses/modeling-a-sci-fi-helmet-in-blender

The rest as Martin says is practicing a lot, letting your brain adapt to the puzzle that is edge flows and trying to make something all quad.