The best way to know if the sago pearls are done thoroughly is by making sure there are no white dots in the pot. When thoroughly cooked, the sago pearls will be totally translucent. When not fully cooked, you will see a small white dot in the center of the pearls. There will be a lot of starch in the pot as you cook the sago, so you will not really be able to see the pearls individually. That is perfectly fine, all you need to do is make sure there are not white dots in it. If there are, continue on the heat until the mixture turns completely translucent.