Verbs:

Action: add -ing.

Auxillary: am, is, are, was were, --present/past progressive
do, does, did
have, has, had -- with past participle, present and past perfect.
shall, should, will, would, can, could
may, might, must -- models
be (infinitave) being (present participle), been (past participle)

Linking: all to be verbs (am, is, are, was, were, be, being, been)
any of the five senses: smell, look, seem, appear, sound, taste, feel.