The uninitiated would tell you to put your lights away sensibly. But anyone who knows better, knows that it doesn't matter how sensibly you put them away. Once they're in the box, its a boxed up free for all for 11 months.
Step 1: Choose your Christmas Spirit (mine is Vodka) Step 2: Find the free end you're going to start with, it doesn't matter which free end you start with, only that you stand by your choice throughout the entire process. You can't change your mind halfway through, even if it looks like you chose wrong. Changing your mind will set you back. Hours. Step 3: Loosen knots, be gentle, feed the end you started with through the tangles - this is where you'll break bulbs if you aren't a seasoned pro. Have bulbs on hand. Step 4: Have some Christmas Spirit! Step 5: Repeat as necessary.
Once you have a strand sorted - lay it out far far away from the others. They're like headphones. And ducklings. They'll clump together and you'll never work it out.