I'm a big proponent of quality tweezers, ones that are designed for production use. You want tweezers that will hold but not damage the decal. In many cases the tweezers must hold the decal itself not the backing paper, so you want a pair that can do it without tearing or otherwise damaging the decal.
You also want a tweezers that has the ability to get under a decal without scrunching up the edge and creasing it. Reverse action tweezers with ultra fine points are perfect for decaling.
Here is a video I made that you might find useful.