There is this neat little thing that all brand new aspiring card magicians seem to do with a deck of cards. It's like a tell I suppose. The would be magician holds a deck of cards. Then start talking about something that is meant to lead in to some sort of effect. As they are talking they do this; their hands swing way out and way in again pivoting at the elbow while holding the deck. They also seem to reach over top of the deck while in hand and squeeze it for no reason. If they hold a single card away from the deck, the same back and forth swinging occurs. It's truly fascinating to watch.
Beyond this, there is a customary death grip that starts early on and seems to take a very long time to loosen up. THIS is where I think most magicians lose track of their handling of things. The only way to develop a touch and handle cards with some level of grace is to loosen the grip on the cards. The lighter you can hold the deck and execute techniques, the better your magic will look. Or at least the more effortless it will appear.
I think of push through shuffles and pull out shuffles with this in mind. People have crazy strong grips on the deck and in the process it makes the technique look broken up and chunky. It also makes it VERY difficult to execute the moves with any degree of smoothness. The tightness in the hands and the deck also telegraph that something is happening. The tight grip reduced the speed of the move as well. Overall, a tight shuffle, tight grip, and tight hold on the deck will result in a less deceptive, awkward, heavy looking move. It will look like a move.
Try to be gentle, try to hold the cards as little as possible. Let them move around and wiggle in the hands. Learn to create little cages with your fingers so that your cards can move about but will ultimately be stopped again when they hit the side or tip of a finger. You can keep the cards under tremendous control this way and it will look and feel very open and free.
Hold your cards lightly! Shuffle gently, cage the cards, and lighten up!