A bunch of quite useful tricks. Some I already used and other's are new. Here are the headings:

1. Forward Yubikey Agent
2. Reuse connections
3. SSH straight into tmux
4. Alias commonly used hosts
5. Do not add testing stuff to ~/.ssh/known_hosts
6. Make connections last longer
7. Canonicalize hostnames
8. Yubikey and GitHub, without touching it every time

I find it quite helpful to create a persistent connection to github. It greatly reduces my connection latency for pushing and pulling.