Learning judo at home is problematic. According to former Olympic judo coach Phil Porter, judo is a sport fighting art, similar to wrestling. Without live training with a partner, which should never be done except under qualified coaching and supervision, you won't be able to truly understand any of judo's constituent moves. However, if your schedule or location doesn't allow attending a class, you can get started on the basics by practicing at home.
Set up your training space. You will need a minimum of 200 square feet, cleared of all obstructions and liberally padded. If using your garage for this space, you will need extra padding. The concrete floor makes injuries more common and more severe.
Find basic judo training videos. You can order these from most online video or book stores. Martial arts coach Dave Coffman recommends checking user-generated video sites and the home pages of judo programs. Both are likely to have several useful tip and how-to videos about basic judo moves.
Select a basic judo move or concept, preferably one that doesn't require a partner. Good starting points include forward and rear ukemi, rear and side breakfalls, chops, stances and footwork drills. Focus on one move at a time, practicing it until you feel comfortable before moving on to the next move.
Seek feedback whenever possible. Check for advice and detailed descriptions on forums dedicated to judo. Once you feel comfortable, post videos of yourself performing your judo techniques for other forum members to critique. Although you'll get your share of unavoidable Internet crank comments, you will also get valuable, well-intended advice from fellow practitioners.
Move on to basic throws and locks once you're comfortable with the beginning moves. When practicing a judo throw or lock on your own, it's important to experience both sides of the equation. Spend equal time positioning your body as if applying the move, and positioning your body as if having the move applied on you. As martial arts grand master Bruce Juchnik says in his video on throwing techniques, "If you want to learn to throw somebody else, throw yourself."
Avoid choking techniques unless you have the assistance of an experienced judoka. Judo uses both blood and air chokes to safely incapacitate an opponent or attacker, but it's easy to cause damage or death if you perform these chokes incorrectly.