I could talk all day about what a "proper release" should feel like, but at impact the swing is moving too fast for most golfers to change old habits. What works better is throwing a Frisbee for 10 minutes. The fast, fluid snap is just the feeling you want to experience.
For right-handed players, take your normal golf stance with a Frisbee in your right hand. Backhanded is the more common throwing method, but this drill requires the forehand style, where you position your thumb on the inside edge of the disc. Throw it as if you were hitting a shot right-arm only. The goal is simply to achieve a tight spiral. (If you want to get advanced, work on draws and fades, which translates in golf.)
If the Frisbee dives straight into the ground, don't worry. Chances are you're like most amateurs who unhinge their wrists too early in the downswing. Keep trying until you can throw the 'bee 30 or 40 yards. You'll train your right wrist to hold its angle into impact and gain tons of distance.