I recommend you to read the
official FAQ on the DosBox site.
Basic Setup and Installation
Command Line
Z instead of C at the command prompt
Internal Programs (important, especially MOUNT)
Most of the stuff in there is not really needed, but you would do best to familiarize yourself with the specific topics I linked to.
The mounting of your DosBox games directory, switching the promt to the emulated C: drive and clearing the screen from previous commands can all be executed from the [autoexec] section of
dosbox.conf, so you won't have to re-type them every time round.
Frontend programs can help running DosBox with varying configurations for different games.