I had the pleasure in this segment of my TV show to work with a great Italian craftsman (I think tiles are in Italian's blood) on a floor tile job. The still picture you see here doesn't do it justice, but this is one of the tips I learned from Fior Paolucci of Trades Unlimited in Richmond Hill, Ontario. When you want to move a tile just a little bit in wet mastic or mortar, it just wants to slide back to where it was. The trick to move it just a little bit is to "tap" it with a sliding motion of your fingers, little sideways hits, to jerk it along just a little bit. This jerky motion will actually move the tile in little increments that don't bounce back.