I always start tmux using in a shell function like this

    tms () {
          session_name="${1:-sean}" 
          tmux new-session -A -s "${session_name}"
    }

What that does is create a new session or attach to one if it exists. This makes it really easy to detach a session or to log into the same session in multiple windows or whatever.

I can pass a name for the session but if I don't it defaults to my name (so when I'm on a multi-user box my session doesn't clash with other people's). This makes it easy to have separate "work" and "personal" sessions or whatever.

I think for "tmux new-session -A" to work you need a reasonably recent tmux but anything from the last couple of years or so should work.