Boy, have I wondered about this one!
Some NDEs I've read just don't seem like they line up with scripture AT ALL. While others seem different than "what I've always believed", yet I can go to the scriptures and see how it could fit, maybe just something I haven't understood before.
For me, it can't be anything that's seems clearly against the scriptures (given that I don't understand it all, have my own mis-interpretations, etc.). Here an example of a "red flag! this is clearly against scripture"; "the light told me it's really OK that I murdered someone, mankind will one day understand this".
Here's one that's more like, "well, maybe this is just something I haven't fully as yet understood"; "everytime I called the name of Jesus, I was drawn back up to the Light and felt love and forgiveness. As soon as I recognized I needed a Savior and called on Him, my judgment was over. It was a matter of minutes, not years".