This isn't a discussion of great techniques, or esoteric thoughts on budo wisdom, but in the day-to-day life of martial artist, it can be important. What's the best way to wash your hakama? This is the method I use.
The first question is, is the hakama cotton or tetron or polyester?
If it's cotton, only wash it in cold water. I only wash mine in cold water and mine is tetron, but it's really important if it's cotton.
To wash the hakama, fold it neatly like you are putting it away, roll up the himo and put rubber bands on them to hold them, and then put the whole package in a delicates bag. Wash it in the delicates bag in cold water. This will help maintain the pleates so they are easy to find when you take it out of the washer.
Hang it up to drip dry. Press in the pleats with your fingers while it is still wet, and clip the bottom of each pleat with a clothes pin to help keep the pleats neat.
After it dries, fold it neatly.
If you have a tetron hakama, you probably won't need to iron it more than once or twice a year to keep the pleats looking nice. If you have a cotton hakama, this makes the post-washing ironing process MUCH easier, because the pleats don't vanish in the washing machine.
Happy laundry day!