The modern practice of randori comes from a training method called nokoi ai. This method became popular during the Meiji era in the Kito-Ryu and Tenshin Shin'yo Ryu schools, of which Kano was a student and later a master. The method started with an attack. If the attack was weak or unsuccessful, the receiver was to initiate a counter-attack. If the counter was weak, the partner who started the exchange was to counter, and so on.]
1. Study the correct way of applying the throws. Throwing with brute force is not the correct way of winning in Judo. The most important thing is to win with superior technique. (Yamashita Yoshiaki, 10th dan) Seek to generate hazumi (momentum), not ikioi (impetus). Hazumi relies on skill, ikioi on strength.
2. First practice offense. You will see that defense is included in offense. You will not make progress by practicing defensiveness first. (Yamashita Yoshiaki, 10th dan)
3. Practice your throws by moving your body as freely as possible in all directions. Do not lean to one side or stand stiffly. (Yamashita Yoshiaki, 10th dan)
4. Kano Jigoro told us in his lectures that the purpose of randori is to train the mind. Yamashita Yoshiaki (10th dan, and Kano's usual uke) told his students that technique and mind are just like the front and back of one's hand; they are two sides of the same thing..
5. Nakano Shogo (9th dan) could throw most people at will from any direction, any grip, and any entry. His favorite throw was uchimata. He was asked how it was that he was able to use a throw that appeared so specialized against such a wide array of opponents and situations. He answered, "... this is the result of my practice of happo akehanashi ("leaving the door open in all directions") which means that whenever I practiced with my opponent I always let him freely seize any part of my Judogi he liked, and afterwards I never refused an practice partner's proposal. There has never yet been a practice partner that I didn't like!"
6. "The soft controls the hard." -- old Jujutsu saying from the Tao Te Ching of Lao tzu (Li Erh).
7. "Mind/spirit, and technique unite in seiken setsutan (brief moment of intensity). Mind and technique are like flint and steel: uniting them slowly brings no spark." (Nagaoka Hidekazu, 10th dan)
8. Find the gap (kega no komyo). Find the opponent's lapse (crevice, interval). By the same token, maintain mizu no kokoro (mind like water), keeping calm and the mind undisturbed. This is fudoshin or "unshakeable mind"); robbing the opponent of his "spirit," causing a gap or shishin ("stopped mind").
9. Take advantage of your opponent's excitement or confusion. Take advantage in moments of i-tsuku, when your opponent's intention stops. Take advantage of your opponent's failed technique, imperfect posture, or tsukuri.
10. Don't restore your opponent's posture. That is, don't retract your kuzushi; extend your kuzushi throughout the technique.
11. Enjoy the spirit of your partner in randori, as in other practice. Do not let the opponent take your mind. (Aiki)
12. The emphasis is first on throwing techniques. Throwing practice is more valuable to both physical and spiritual training. Becoming too involved in grappling early in one's training makes it unlikely that nage-waza will be mastered. (Kano Jigoro)
13. The fundamental body position in randori is shizentai. The natural posture is most flexible and adaptable to a changing opponent. It is also the least tiring—battles can last a long time.
14. When engaged in randori with a student, it is considered unethical to apply techniques that have not been presented to the student.
15. When engaging in randori with a junior partner, always employ the method of mo sukoshi, or "a little more." That is, when in randori with a shodan, apply your techniques and attacks as if you were nidan. With the sankyu student, be nikyu. This is more engaging for the junior partner, and makes for better teaching opportunities.
16. Always keep in mind that randori is training in the art of attack and defense. In a martial art, it is essential to train the body to move freely and agilely to deal with punching and kicking attacks and to nurture the ability to react quickly and skillfully.