Tips:

1. Its better if you install MJ Polytools before jumping into modeling, as its very handy for modeling and has been a great help for all Maya modelers.

2. I always model my characters using Smooth Proxy, so that I can work on my lowpoly half and see my smooth half as how it is going to be when smoothed.

Unwrapping

At this stage I unwrap the complete model and arrange it properly, keeping my texturing needs in mind. So that I don't face any problems later while he is rigged or when I will be texturing him. Also note that it is important to unwrap your model before getting into Zbrush detailing. I mostly use Wings3D for unwrapping my most models and use planar mapping in Maya. Then export uvs at higher resolution of 4000 pix.