Taking care of a baby tortoise is easy. These are the important points:
Food and Drink
Baby tortoises should be given more or less the same food as you feed adult tortoises, just in smaller quantities. Stick to slightly softer foods like weeds, dandelions and lettuce, until their jaw strengthens. The young tortoises should get all the water they need from their food, but it is good to have water available for them in a very shallow dish. The key point is not to overfeed them as that causes the shell to grow unevenly causing “pyramiding”.
When to hibernate your tortoise is a matter of choice. Some breeders suggest hibernating them after a year, but I prefer to wait until they are 4 or 5 years old. Until they have grown in size they have probably not managed to store enough fat and water to sustain them through the hibernation period. The Jackson Ratio is a graph which shows the length (along the bottom of the tortoise, not over the top) to weight ratio which a Hermann tortoise must have achieved before it can be safely hibernated.
The Tortoise Trust has an excellent and comprehensive guide to hibernating your tortoise which can be found here