Learn through simple practice. Adapting specific techniques and/or forms will ultimately reduce your ability to understand how and why they're available for proper use, diminishing your ability to creatively produce a piece of art.
In referral to learning forms and understanding how realism is properly displayed in 2D imagery, refer to Tophius's guidelines. Regardless of the fact that he obviously has yet to master what he's out to accomplish(no insult intended), he's definitely on the right track.
