Here is a list of skills to develop before practicing judo none of which is mandatory with exception of #1 you really need to get that one in check.
1.Dialing numbers on your phone or searching the web for practice details.
Practice dialing your phone so you can find out where and when the class is. Then practice getting to class so you can practice judo. Google is a good idea too or DuckDuckGo or Bing and Yahoo search, if you are in the 90’ search engine mood.
Or ask a friend, sensei fellow judoka, but without this specific skill set it is hardly possible to start practicing judo.
2.Get yourself into gripping mood.
While you don’t want to get into the habit of always just grabbing tightly, you do however want to be able to hold on to someone when it makes sense in the heat of grip fighting, and grip fighting is a big part of jacketed grappling, especially Judo. So you might develop your grip strength and endurance and start to learn the gripping skills if you have a chance
3.Get used to being on ground a lot, and getting up and getting down again.
If you do not want to find your progress hampered by anything you should get comfortable with the ground. By that I mean getting comfortable falling, rolling, moving from place to place, using your hips and legs together properly, getting from one position to another, and learning to calm air when being smothered by someone laying on top of you in ne waza.
4.Be a bit of a cardio freak
Get your body ready for increased heart rate activity. Do lots of cardio to get your endurance up this not mandatory, but it will make your progres much faster, you not fighting for breath after warm up session will be an asset. Learning judo means positioning a specific body part at a specific time in a specific manner takes concentration and you need that O2 delivered as fast as possible to gray cells up there.
No need for power lifting, but get your overall physical strength up. There’s an old saying martial arts that “size doesn’t matter”. That’s a misleading statement and it’s only somewhat valid if you take a small (experience) practitioner against a larger (unskilled) opponent. Apples to apples the person who is stronger and bigger has an advantage in pretty much any combat art.
6.Do some yoga or stuff
Flexibility and mobility are important. Start stretching to increase your overall range of motion. When you are more flexible you’ll be faster, be able to properly perform a wider range of techniques, and be less prone to injuries.
7.Last but not the least be persistent!
Remember, it takes time to learn this stuff, it sometimes can feel like learning to walk again after a massive stroke. At first it will be hard and you will feel frustrated or silly, it is OK. Jigoro Kano once said: “If there is effort there is always accomplishment” .