Practicing adjectives in Icelandic grammar is an essential part of mastering the language. Icelandic, much like other Germanic languages, tends to assign gender, case, and number to its adjectives. Therefore, the exercises should aim to perfect the student’s usage of these attributes in various contexts.

The first exercise may involve matching adjectives to nouns of different genders – masculine, feminine, and neuter. This practice helps students understand the adjective-noun agreement in terms of gender. For example, the word for “big” changes as “stór”, “stórt”, and “stór” in masculine, neuter, and feminine respectively.

Next, students should work on declension of adjectives according to the grammatical case – nominative, accusative, dative, and genitive. In addition to basic exercises such as fill-in-the-blanks and sentence formation, advanced exercises could incorporate reading comprehension. Such exercises could include texts where students must identify and correct the misused declension of adjectives.

Lastly, the use of comparative and superlative forms of adjectives can be practiced. Icelandic has both regular and irregular forms. Hence, exercises should drill students on both. True-false exercises or crossword puzzles can be fun ways to learn these forms.

In essence, adjectives exercises in Icelandic grammar should be diverse and follow a progressive path, starting from basic gender agreement to more advanced exercises like declension and degrees comparison.