The ablative case has a whole range of jobs in Latin. As with the dative, my advice is to keep the basic meanings of "by/with/from" in your head, and then to think on your feet as your meet different examples. If classifying the different roles of this case helps you learn, then read on; if not, stick with ‘by/with/from’ and see how you go.

Ablative of Means -  How did he write? With great care: magna cura.

Ablative of Manner  - With what did he write? With his own pen: suo stilo

Ablative of Agent - With passive verbs.

Ablatives are used to describe aspects of Place and Time.

Ablatives are also used with certain prepositions.