I use tmux a lot for handling different sessions. What is annoying that everytime when I ssh to a machine a first need to run the command to open the tmux session.

Here is a simple config so that when you login into ssh it will immediately run the tmux command so that you don't have to type it yourself after login. Saves you a couple of seconds with every login :)

Edit your $HOME/.ssh/config and add the "remotecommand" for the host that you are loggin into:

AddKeysToAgent yes
Host myspecialhost.nl
        RemoteCommand /opt/local/bin/tmux new -A -s chat

Now do a ssh leon@myspecialhost.nl it will do the command.