You can customize the beginning and ending code that your slicer adds to the gcode files it produces to automate certain tasks or produce a more desired behavior. Below are suggestions for these codes. Feel free to use them and modify them to fit your usage. For a list of gcode commands and their usage, see this page: http://reprap.org/wiki/G-code
G28 ;home all axes
The following ending gcode will lift the Z axis slightly, retract filament to reduce oozing when pre-heating for the next print, move the bed to the front, and run the extruder cooling fan at 100% for 2 minutes before turning it off.
M104 S0 ;extruder heater off M140 S0 ;bed heater off G91 ;relative positioning G1 E-1 F300 ;retract the filament 1mm G1 Z+0.5 E-3 X-20 Y-20 F6000 ;move Z up and retract filament 3mm M106 S255 ;fan at 100% to cool nozzle G90 ;absolute positioning G28 X0 Y0 ;home X and Y G1 Y190 ;move bed forward M84 ;steppers off G4 P120000 ;wait 2 minutes (120 seconds) M106 S0 ;fan off