All the tutorials I have now are about deforming one single object (a hand, a foot). But I have characters composed from multiple objects: hands, hair, clothes etc. How can I deform the entire character? Link individual objects with the armature? Joining all the objects in a single mesh?
I’m not much past a beginner but basically you can do all three.
In many cases the whole body is one complete mesh - for a humanoid or organic character. The eyes, teeth and similar things may be separate objects, though not always, and the clothes would usually be separate, though not always. The armature would usually contain all the bones needed for all parts then all things can be parented to the same armature to ensure they all move together.
I think the reason tutorials focus on hands and feet is because these are the most complex parts to build and animate, especially in the older versions of Blender. They often involve a variety of constraints, mainly IK and Action constraints to make them operate the way people like them.
You can even build your armature in separate sections and join those into one armature if that makes it easier.
You also have shape keys (RVKs) to play with to add subtle animations if you like.