My new Dell XPS 12 Ultrabook is VERY prone to screen ghosting, even after being left for only 10 minutes.
Straight to the point, I use this tool for about 5-10 minutes when I’m not using the laptop.
http://www.gribble.org/lcdfix/index.html
P.S It instructs you to use it 24 hours but in reality, if your screen takes just 5 minutes to be affected by ghosting then it will take 5 minutes to fix/get rid off.