Three introductory videos for judo:

Seiryoku Zenyo Kokumin Taiiku No Kata – Solo Drills Only
“Maximum Efficiency Physical Education Kata” – Kano sensei was a teacher and he developed this kata as a way to warm up the body and also to help develop movement and stability before demanding strenuous activity.

Judo-style 20-20-20
A 20-20-20 is a classic warm up exercise or mid-session cardio training consisting of 20 squats, 20 push-ups, and 20 sit-ups. This version calls for “jigotai” (defensive posture) squats, judo-style push-ups (scoop downward with your chest, forward then backward), and floating-heel sit-ups (keep your heels just off the ground and your head up, scrunch into a ball balanced on your butt, flatten all the way out).

Ukemi-waza (breakfall techniques)
You have to learn how to fall correctly before you can learn how to throw. If you’re not afraid to take a fall, you aren’t afraid to try throwing. Also, this it possibly the single most frequently used aspect of judo training. If you can fall correctly, you will minimize injury, and this is an excellent tool to have your whole life. This sequence progresses from basic technique of how to slap properly up to taking a full fall to the left or right. (Only zenpo-kaiten ukemi, rolling breakfalls, are missing, which I didn’t have room to film in my little bedroom space.)