Learning to count cards
When I used to play Bridge regularly, I started out simply by keeping track of suit counts.  How many have been played from each suit.  I then added counts for Aces and Kings, keeping track of those on top of the suit counts.  I then expanded into tracking all of the trump suit, and followed by tracking the remaining suits.  If you play regularly and take a gradual approach, it will eventually become second nature, but it does require regular play.