How do I build muscles of the upper part of my body?
Short version: train your upper body consistently and mercilessly
Long version is practically the same. My unique angle is that I use only bodyweight exercises: pushups and pullups.
Take a look at my photos below. If you are OK with such results, my workout regime is as simple as dull. I do one consecutive series of pushups and one of pullups to the point of failure every single day.
End of formula ;)
It cannot get simpler than that.
My workout is the result of my lack of time. I prefer to read or write than exercise, so I limited my workout time to a bare minimum.
The photos show my musculature after 6+ years of doing pushups and about 2 years of doing pullups.
My chest could use some development, but its look is partly a case of my individual brawn and partly the result of my regime. Pushups, which I’ve been training much longer, are very good for arms, less so for chest.
Speaking of pushups, after a year or so I was doing over 100 consecutive pushups, so I switched to different (and more difficult) variations: legs-elevated, wide-grip, narrow-grip, diamond, archer’s and so on. It helped not only with time commitment, but made my workouts less monotonous and trained other muscle segments.
PS. I avoid gyms. Developing an impressive musculature is not my priority and gym trips consume a weeeeell too much of my precious time.