Common suffixes that form adjectives include: -able (comfortable), -al (musical), -y (cloudy), -ous (famous) and -ive (attractive).
A ‣ -al 
Adjectives ending -al are usually formed from nouns, and often mean ‘relating to the noun’ , e.g. a musical instrument (from music), a political issue (from politics), an electrical fault (related to electricity), a personal opinion (the opinion of one person).
SHICHI-GO-SAN
Shichi-Go-San (meaning 7, 5, 3) is an annual ceremony in Japan for three-and seven-year-old girls, and three-and five-year-old boys. It is on November 15, but it is not a national1 holiday, so people often have it on the nearest weekend. Seven, five and three are seen as important years in the growth of a child, and the numbers also have cultural significance2 because odd numbers (1, 3, 5, 7, 9, etc.) are lucky in Japan. This is one of the special days when the older boys and girls are allowed to wear traditional3 clothes: a kimono for girls and hakama trousers for boys. Now it is quite normal4 for children to wear western-style clothes at this ceremony. The children visit a shrine and are then given special sweets called Chitose-Ame by their parents.
1 a holiday for the whole country
2 they are important in Japanese culture
3 in a style that has continued for many years
4 usual
B ‣ -able /əbl/
This suffix forms adjectives from nouns and verbs, and the prefix un- often forms the opposite:
an enjoyable party [something that you enjoyed]
a comfortable chair (opp uncomfortable)
a suitable word or phrase [right/correct for a particular situation; opp unsuitable]
a reliable service; reliable information [able to be trusted or believed; opp unreliable]
fashionable clothes [popular now with many people; opp unfashionable]
a reasonable decision or price [fair; not a bad decision or price; opp unreasonable]
a sociable person [enjoys being with people; opp unsociable]
Sometimes the opposite form is the more common adjective:
an unforgettable experience [something that cannot be forgotten]
an unbelievable story [something that is very surprising and very difficult to believe]
C ‣ -ful and -less 
The suffix -ful often means ‘full of’ or ‘having the quality of the noun’, e.g. a colourful room has a lot of colour in it; a helpful person gives a lot of help; a peaceful place is calm and quiet.
The opposite meaning is sometimes formed by adding the suffix -less to the noun.
a useful machine [having a lot of uses; opp a useless machine]
a painful injection [giving pain and being unpleasant; opp a painless injection]
a careful driver [drives with care and attention; opp a careless driver]
Common mistakes
The suffix is -ful (NOT full), so useful and careful (NOT usefull or carefull).