How to make mozzarella with rennet? I used to make soft cheese by vinegar, which quickly results in the formation of curd. I tried to make hard cheese (mozzarella) by rennet (commercial tablet) by the process took more than 30min and the result was something like yogurt.

I simply followed the manual (mixing the tablet solved in warm water with the milk at temperature 35 - 40 C). Was something wrong with my procedure, milk, or rennet?
The one time I made mozzarella, I used this recipe. As I understand it, the key is (a) citric acid, and (b) kneading (that's what gives it the stringy texture). It turned out pretty well, but it didn't keep long at all.