Ward's answer is great if you want to set your title based on what host you're on etc every time you open a terminal. If you just want to quickly set a title though, you can just run echo by itself:
echo -ne "\033]0;SOME TITLE HERE\007"
or make a simple function (inside your ~/.bashrc
), say termtitle
termtitle() { printf "\033]0;$*\007"; }
which you can run with termtitle some title here
.