if you ARE going to work on high poly, then here's how i go about it:
first thing you need to do is block out all the big forms and shapes. get your proportions right, and look at the silouhette. this is the outline of your model, no details are even thought about yet, let alone finalised. this is honestly the most fun part of the model, because whether you have a concept to follow or not you can still pretty much go nuts and make any shapes you want.
Here is where i start to tidy up, still nothing more than big forms, no real detail.
here is where the detail starts to come in.
tightening up the bigger details
starting the finer details.
finishing the finer details.
remember, at every stage of subdivision you should be getting the most out of every polygon and vertex to define something.