Belaying is not the most straightforward activity in the world. To get good at it, you are going to need a lot of practice and experience. Very little in the world can replace experience, but to get that experience, you must belay as much as you possibly can. Along the way, you will develop some tendencies and learn your craft.
But, all in the meanwhile, there are subtle steps that you could be taken to improve your belaying skills. For starters, consider investing in some belay gloves as gripping the rope can chafe your hands and cause discomfort.
Gloves can prevent rope burns and provide you with a superior grip. Also, whenever you are not feeding slack to the leader, be sure that your other hand is in the locked position. Another area is at the beginning as when the climber is low to the ground, ensure that you do not have excess rope out as you do not want them to hit the deck.