Here are three beginning conditions that will help your beginner friend acquire successful "Sleeper" skills quickly:
1. Use a 100% cotton string and use a fresh string. The cotton string is a good shock absorber and a fresh cotton string is the best shock absorber. Be sure the loop at the axle is loose almost to the point where the YoYo won't return.
2. Attach the string with a slip loop to the middle finger just behind the first joint, not at the base of the finger.
3. Relax.
And here is a step-by-step procedure for practice:
1. Curl the YoYo finger around the YoYo groove. The inside of the finger from the base to the tip should be in comfortable contact with the YoYo. The string must lead (from the slip loop at the inside lateral center of the finger) away from the palm to the YoYo groove, with little or no slack. Rest the inside edge of the thumb at the YoYo groove.
2. Start with the upper arm vertical, elbow loosely at the side. Bring the forearm horizontally straight to the front, hand closed loosely with the palm facing up. Adjust the wrist to bring the YoYo groove vertical (Important!) and in line with the forearm (also Important!).
3. Bring the forearm up, moving the elbow slightly out front to place the YoYo hand at shoulder level (YoYo groove still vertical and in line with the forearm).
4. In a coordinated movement, move the elbow to the rear, let the forearm fall outward and downward, and let the wrist rotate forward while opening the hand. Consciously aim to make the string hang over the tip of the extended YoYo finger (palm upturned) as the YoYo descends to the end of the string. (For an excellent reference to this fingertip control technique, see your bookstore and order a copy of "Stop-Time", Frank Conroy, Penguin Books 1977-1987, pgs. 108-111.)
5. As the YoYo moves to the end of the string, avoid pulling back on the string. Just ease off the downward motion of the hand and let the YoYo finger act as a shock absorber.
6. With the YoYo "sleeping" at the end of the string, a tug on the string can start the YoYo back up to the hand. Before or after the tug, turn the hand over to face the palm down and catch the YoYo.
Refer to the preceding article "Getting Started With a Smile" if at the tug the YoYo won't grab the string to return to the hand. Chances are the loop at the fixed axle is too loose, or the transaxle setup needs attention. And of course the YoYo must still be spinning fast enough for the tug to succeed!
If the YoYo refuses to sleep, chances are the loop at the fixed axle is too tight (so get some of the excess twist out of the string) or the transaxle setup needs attention. And it may be that the YoYo has been thrown too hard, producing a shock that bounces it back from the end of the string. Practice avoiding that shock before trying to throw the YoYo hard for a long spin.
When (with easy, relaxed throws) your beginner friend is getting the YoYo to sleep on nearly every throw it may be time to move on to the next objective: the "Five Second Sleeper". Build up the "sleep" time with practice to five seconds; audibly count off "one - one thousand, two - one thousand, . . ." Longer spins come with practice, and transaxle YoYos help a lot.
A final word few words: One of the reasons for aiming to hit the end of the upturned finger with the YoYo string (at Step 4, above) is to release the YoYo with the groove vertical so that it will "sleep" with the groove vertical at the end of the string. Spinning vertically the YoYo avoids contact with the spinning sides of the YoYo and will spin longer. Contact with either spinning side will cause the YoYo to rotate and tilt at the end of the string; the YoYo then proceeds quickly to "die" rather than "sleep"! Recheck each part of your technique and practice for that straight vertical throw and spin.
Practice, have fun --- and get some sleep!