I always hated having to get up from my bed, turn off my lights, then stumble over all the stuff on my floor as I went back to bed. This simple solution takes 5 to 10 minutes, and can be done with stuff from around the house.
Step 1: Prepare Your String
Tie a small loop that will fit over the light switch in the string near then end, and tie the heavy thing to the string 3-4 inches from the end.
Step 2: Loop the String Over the Switch
Loop the string over the switch.
Step 3: Secure It With Sticky Tack
Secure the string to the switch with sticky tack.
Step 4: Use the Thumb Tacks As Makeshift Pulleys
Then attach the end of the string to the wall with another thumb tack
Video of it in action: