A useful trick in vim is an editable command mode with previous commands in the buffer. To get to this mode go to normal mode (ie. hit ESC) and then type q: this places you in editable command mode. If you always want to go to that mode you can remap : with the following command:

" Always go to history mode
nnoremap : q:i
nnoremap / q/i
nnoremap ? q?i

Happy Hacking!