Consonant suffixes

Suffixes beginning with consonants do not often cause spelling problems: usually you tack them on to the end of a word without altering it: sincere + ly = sincerely
Exception: words ending in le change the le to ly: able/ably, subtle/subtly
Other exceptions: fully, truly, duly, wholly, argument
Common consonant suffixes are: ful, ness, ment, some, tion, sion, ly

Compliment and Complement

Both these can be used as nouns or verbs.
Compliment is the more common. It means to praise someone: He complimented her on her writing.
Complement means to add on and improve: The belt complemented her outfit. To remember the spelling, think of the word complete.

Prefixes

Prefixes are syllables which add on to the start of a word to change its meaning.
Usually you tack them on without any alteration: dis + appear = disappear 
Keep any double letters that result: dis + satisfaction = dissatisfaction

Common prefixes are: dis, un, mis, re, al (not all), pre, bi, semi, tri, ex, inter, post, trans

Some prefixes change their first letter to make the words easier to pronounce:
in + legal + illegal   in + mature = immature   sub + fix = suffix