Our first grammar section this year was MODALITY. We have been taught in a special way, it was the thinking approach. First of all, you make hypothesis about several modal verbs.
This is an example of our first "try":
Then we got to another more specific table by analyzing exercises and accumulating examples. This is an example of classwork on modal verbs.
As a result I came up to an algorithm of choosing the wight modal verb.
This is my own way of understanding differences in modal verbs, but it helps. As a result, most exercises are correct! Hope it will help you : )
Here are some exercises, which I mostly fail:
Extra exercises on modal verbs,which are really good,you can find here : http://www.englishpage.com/modals/modalintro.html