$ git branch my_feature   # Creating the branch  
$ git checkout my_feature   # Changing the codebase so that we're on that branch now  
$ git checkout -b my_feature   # This does the two previous operations in one ;)  
$ git add file1 file2  
$ git commit -m "Meaningful commit message"   # We didn't just commit this on the master branch like last time, but on the my_feature one  
$ git add .  
$ git commit -m "Other meaningful commit message"  
$ git push origin my_feature   # Notice: we're not pushing master anymore, you just create a new remote branch