When talking about adjectives we should also talk about comparative
and superlative adjectives. Here you have all the information you need
to know to form them.

Comparison of Adjectives. Click here for printing a document with all the information.

the following websites you can also find information about how we form
the comparative and superlative adjectives in English, as well as
exercises for practise. I hope everything is useful for you.

Comparison of adjectives, a webpage with explanation and many exercises.
Video: comparison of adjectives, grammar explanation by the British Council and some links to related pages.