SSH keypair setup for GitHub (or GitHub/GitLab/BitBucket, etc, etc)
Create a repo.
Make sure there is at least one file in it (even just the README.md)
Generate a SSH key pair (private/public):
ssh-keygen -t rsa -C "firstname.lastname@example.org"
The git command-line utility has plenty of inconsistencies http://steveko.wordpress.com/2012/02/24/10-things-i-hate-about-git/
A GUI like http://sourcetreeapp.com is often helpful, but staying on the command line usually quicker. This is a list of the commands I use most frequently, listed by functional category:
git status list which (unstaged) files have changed