Beginner level

-ise/-ize (usually changes nouns into verbs)

-fy (usually changes nouns into verbs)
ADVERB SUFFIXES

-ly (usually changes adjectives into adverbs, but also some nouns into adjectives)
-ful (usually changes nouns into adjectives)
-able/-ible (usually changes verbs into adjectives)
-hood (usually class-maintaining, with the word class remaining a noun)
-ess (usually class-maintaining, with the word class remaining a noun)
-ness (usually changes adjectives into nouns)
-less (usually changes nouns into adjectives)
-ism (usually class-maintaining, with the word class remaining a noun)
-ment (usually changes verbs into nouns)
-ist (usually class-maintaining, with the word class remaining a noun)
-al (usually changes nouns into adjectives)
-ish (usually changes nouns into adjectives/ class-maintaining, with the word class remaining an adjective)