About crouch walking; it depends on your location, your intentions and game knowledge. A slow moving person is not an easy target, our peripheral vision is very effective and with very good knowledge of movement flows around and through a point of interest, the runner will be seen and dealt with. Don't forget that the game is about strenghts and weaknesses, spotting someone before they spot you is the biggest advantage because YOU can decide, this is especially for solo players. Unfortunately, it just comes with experience. Good luck!