To ensure your home is lit for security, make two plans for each room - one plan for when you're at home and another for when you're away.  You can avoid scrambling to find timers by installing plug-in timers, program them for your vacation lighting plan but set them to "manual".  That way, when you're getting ready for vacation, they're already in place.  Flip the switch, and leave.  For safety and security, leave main exterior lights on timers all the time.  Here's a sample lighting plan, including times for vacation settings:

Interior Timers

First Floor:
Living room - light on 5-10:30 pm.
Kitchen - light on 5-7 pm., radio or television on for two hours in the evening.
Second Floor:
Bedroom - light on 7-7:30pm., again 9-11 pm.
Bathroom - light on 10-10:30 pm., and once again sometime during the night.

Interior Sensors:
Basement entrance - light activated by motion sensor at top of stairs.
Garage Entry Into House - light activated by motion sensor.
Living Room - light activated by motion sensor when the timer isn't on.

Exterior Timers:
Front Door - light on at dusk, off at midnight (If the front of your home is not illuminated by a streetlight, leave this light on all night or install a photoelectric cell).
Post Light - on at dusk, off at bedtime (or install a photoelectric cell).
Backyard - low-voltage lights on at dusk, off at 10:30 pm.

Exterior Sensors
Back door, front of garage, shed doors, and under corner eaves: install photoelectric sensors.

Remember, light can be a burglar's worst enemy! Try to make these improvements to your home's security lighting as quickly as possible.