My suggestion is that you can fold it anyhow you want but try to minimise the wrinkles. This will also show others how tidy you are. The next couple of pictures and bullet points illustrate how to fold a gi the way I learned it.
But before I get comments about how dirty my gi is as opposed to what I'm preaching above, please note that my gi is white and clean, I just photoshopped the images to emphasize the folds better ;).
- Step one: put the jacket down onto the tatami (or any other clean surface) as shown.
- Step two: Put the bottom of the gi on top of the jacket at its middle.
- Step thee: Fold one side of the jacket onto the bottom and fold half of the sleeve back.
- Step four: Do the same with the other side of the jacket.
- Step five: Now fold the bottom part of the gi bottom up.
- Step six: Fold the bottom up once again.
- Step seven: Repeat this for again, and it will look pretty nice as the last fold will just fit on the rest of the gi.
- Step eight: Wrap your belt around your folded gi and tuck the end of it below the already wrapped belt sections.