This is a guest post by TT reader Nick Bell (who goes by lebkin in the comments). It’s brilliantly simple, and it speaks for itself.
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Because being a GM is like using a 150 watt bulb, it is easy to get lost in your self-created sea of knowledge where everything seems perfectly clear. To counter this, one needs to build up a set of tools in order to understand the players’ views on what is going on in-game. The best tool is actually the players themselves. Simply put, you can find out what the players remember by stealing their flashlight.

In order to do this, simply wait a few days after a gaming session, and then ask your players what they remember from the prior session. This will tell you where their flashlight is pointed. They will remember the elements that are important to them, and forget the boring ones. Take the things they remember and focus on them in the next session.
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Sound advice — thanks, Nick!