Don't assume a player knows how to slide.And if they can slide many kids (in my experiences)are never taught correctly.The slide for all kids below the JV level should be the FEET FIRST figure 4 slide (as described under baserunning).I use a sheet of cardboard(2x4 feet) and I place it 5-12 feet before the base.You have to evaluate their speed prior to this drill in order to place the cardboard properly.Initially do this drill on grass with a "loose" base(one that will move or give as the player slides into it).Also check your league rules for base distance,and set up your(drill)sprint and slide for that distance.OK have your runner at first base in the ready (push off)position and say "TINK"(to represent the sound of the bat)the player sprints to second using a figure 4 slide,with his butt landing ON the cardboard,and the foot sliding over the base.The kids love this drill.I also time all my players during this drill for evaluation purposes,and it adds to the fun.NOTE:If you have a couple of real slow kids,you may want to keep their times a secret,or tell a little white lie on their times so they won't be humiliated or discouraged.Monitor their future times carefully and look for improvement.When they improve,let them know-praise them!