For v4:
First off, you'll need to have a male Tamagotchi in the Kuchi family if you wish to get Kuchipatchi. You will have to treat it decently so it doesn't become a universal character and make sure kindness points is higher than its style or its intelligence points. I recommend you choose Mr. Canvas as a teacher because of this.
My recommendation is that you try and raise its kindness points as much as possible during the time it is a teenager or adult and try to raise its intelligence and style points a little bit too. If you raise the stats enough, you might get a Nonbiritchi!
For v4.5:
You need a male Tamagotchi. It might be easier to get a Hikotchi or Hashitamatchi as a teen first, because they're universal characters. In any case you'll need to treat your Tamagotchi bad enough to get a universal character.
I remember to get the best universal character I treated it perfectly, just didn't earn any skill points (at all) and it had high weight. So if you don't play games at all therefore earning no skill points and having high weight, try sometimes letting the hunger or happiness hearts drop down to 2 as well.