Sinker grip

I put my fingers together in between the 2 seams. Mine gets more run than sink though.

Here you go plus a whole bunch of other pitches.

http://www.thecompletepitcher.com/articles.htm#grips

Thanks Steve!

There is no specific way for all pitchers to be able to throw a sinker action ball. Generally speaking you are looking at a two seam fastball. Now the individuals arm slot, arm action..ect has a lot to do with it. The pitcher should experiment with putting his fingers closer together, more pressure on one or the other fingers, rolling it over (pronation)...ect to see how it works for him.

-Maryland Mud Dogs Baseball

Rightist

I throw a splitter/sinker, I really don't know what it is, but I hold the ball like a 2 seamer with my fingers outside the seams. When I throw, I press down with my index finger (I DON'T turn the wrist inside, like a screwball). It gets a nice bite towards the plate and loses some MPH too.