When 3d modelling, always have images to reference and research topology of similar objects. Try to use both the front and side profile images to work from.
As you research you should keep a folder of images that are useful references from other artists, their 3d head models.
Patch modelling involves building a model in pieces using the create polygon tool. Building the mouth, nose, ears then bringing them all together.
Starting a model from a cube or another basic geometric shape. This is used as a starting block with details added by extrusions, adding edges or edge loops.
Sometimes it’s more beneficial to trace over your model and re-do the topology. There are various tools & methods to perform this. In maya the method involves making an object ‘live’ and then using the quad draw tool under the modeling tool kit.
The modern workflow is to usually start an organic character by sculpting digital in software such as zbrush & mudbox. This allows the artist greater flexibility in design by moving the topology process after the.