Setting the following makes bash erase duplicate commands in your history
I also jack my history size up pretty high too.
export HISTFILESIZE=500000 export HISTSIZE=100000
Another thing that I do is ignore some commands from my history. No need to remember the exit command.
export HISTIGNORE="&:[ ]*:exit"
You definitely want to set histappend. Otherwise, bash overwrites your history when you exit.
shopt -s histappend
Another option that I use is cmdhist. This lets you save multi-line commands to the history as one command.
shopt -s cmdhist