If you know you have scapular winging, then overhead pressing might be contraindicated for you until you fix your scapular positioning. Bill Hartman, Eric Cressey, and Mike Robertson have written some excellent articles on this topic. Here are a few to start reading:
Push-ups, Face Pulls, and Shrugs by Bill Hartman and Mike Robertson
Heal That Hunchback by Mike Robertson
Here's the link to
Eric Cressey's Articles List. Take a look at his
Neanderthal No More and
Shoulder Savers series of articles in addition to any others that catch your interest.
Here's a
blog from Eric about overhead pressing. And another
blog about scapular stabilizers.
There are also a ton of threads in the injury forum where Bill Hartman helps people with scapular winging issues.
Also, consider purchasing Bill Hartman and Mike Robertson's
Inside-Out: The Ultimate Upper Body Warm-up DVD.
I know that's a whole lot of reading, but hopefully it will help you identify what it is you need to focus on to build upper back and overhead strength.