Switch to LED lights. They've come a long way from their early days of blinding color. Not only have they perfected the design, but LEDs last almost a 100 times longer and use 90% less electricity than incandescent bulbs! And you can string ten strands together, a big jump from the old three-strand maximum. That means less extension cords.
Roll your lights into a ball. Like a ball of yarn, roll your string of lights before you start lighting your tree or front porch. Wind your way down the tree or between slats on your front railing, just letting out as much slack as you need. This keeps the lights tangle-free and easy to handle.
Use accessories! Lighting clips for outdoor lights makes setup and takedown a snap. Automatic timers, including light-sensing timers, will save your money on your electric bill while taking care of task of plugging and unplugging lights every day.
Take notes. When you're done lighting, take pictures or narrate a video with your cell phone, explaining to your future-self how you did things. Make little maps with circles and arrows. Use hang-tags on each strand of lights explaining exactly where it goes. And box everything up according to lighting area. Do not trust your memory.