Pincer grip

CoaA pincer grip is the use of the top of thumb and the top of the index finger opposite each other. This grip is useful for picking up very small objects and also develops into a mature tripod grip of a pencil or pen. 
Prerequisites: Early development which precedes this grip is the variety of grips used when children have a rich experience with many different shaped objects. The key development before the pincer grip is that of using the index finger to poke.  Poke into holes of different sizes. poke into playdough. Poke into sand and other textures. These develop awareness of the index finger as well as strengthen it.
Provide construction toys such as lego and other types. If a child is slow to develop the pincer grip provide motivating things to pick up. Maybe currants to eat one at a time, tiny cubes of cheese. If you offer a currant or small raisin to a child with your pincer grip they need to use a pincer grip to extract it from yours. Help them do this. 
Collage activities help too. See  photo for coloured match sticks which require a pincer grip to pick up.