I have been coaching Jr. High for 2 yrs now and I have found that the best way to handoff was by having the recieving kid place his/her left hand down tight against the body and put the hand in an upside down "V" shape with fingers together. If the arm is kept tight to the body during take off then kid handing off (from their right hand) can usually slap it upward into their hand. This also allows for the kid handing off to aim for the leg and the baton will slide up into the hand. This only works if the hand/arm is tight against the body. When we start we usually run the kids in the order they are going to run in the meet and start about 50 meters apart then run at full speed towards the handoff spot. Then we have the kids yell go when they get close. The reciever then looks forward and takes off fast without looking back. As they continue to practice this eventually they dont have to yell go anymore and can do it visually. If worked for us in high school and we ran the 4x1600 in 3:29.8. If it doesnt work there are always other methods.