1) Add -er to one syllable adjectives: colder, warmer, nearer…
2) Add -r to adjectives ending in -e: larger, stranger, wiser…
3) Add -ier to adjectives ending in -y: happier, hairier, fancier…
4) For adjectives ending in consonant-vowel-consonant, double the final consonant: bigger, hotter, thinner…
5) More + adjective for two syllable and longer adjectives: more entertaining, more valuable, more enjoyable…