Favorite every item in your inventory you want to keep. This makes going through your inventory, finding new items you may have looted, a lot easier. This also makes donating a lot easier. Any item that you have favorited, won't show up when you are choosing items to donate.
I think he's also addressing the current issue of items not showing up marked with an ! as new.
I noticed I get the marks with some things but not others. Gear that comes out of a proficiency pack or for completing a project gets the ! mark while loot taken from boxes or NPC drops is still not showing up marked as new. Friend snagged a video of it happening which I'll post up if I can find the thread started in the Tech Support forum.
In the meantime, this is a handy tip for sorting out the new from old; thanks!