If you come to the SALC, you can use these resources to practice:

• Macmillan English Grammar in Context (i G Lb 02.30), Unit 28, pages 132-135. Check your answers in page 233

And here are some links:

• http://www.slideshare.net/giaymilasaracino/grammar-and-vocabulary-for-cambridge-advanced-and-proficiency-1 page 121
  

• http://englishclassminds.wordpress.com/2011/04/30/how-to-make-comparisons-in-english/

• http://www.slideshare.net/davidatrome/comparatives-and-superlatives-12261021

• http://www.englishpractice.com/improve/degree-modifiers-comparatives-superlatives/

• http://www.tinyteflteacher.co.uk/learning-english/grammar/exercises/much-comparatives.htm