This stool will have a different odor. Newborns have to be pottied after every meal and every other usually will have a stool. Also if the tummy is upset, give the kitty a little acidophilus. Nebulizing can be a benefit here to. If a kitten is stopped up, use a pedialyte dilute mix to the milk.
Most breeders overfeed, that is the biggest problem in hand raising.
This will and can cause liver and kidney damage later in life. Owning a scale is the utmost important thing here because it will tell you how much in cc's to feed. The stool will share the rest. The rule of thumb to my knowledge is 1 cc per 3 oz of kitten weight per hour. Lets do the math for a larger kitten lets say 8 ozes on week two.