Cổ động (To launch propaganda): Encourage somebody by following the crowd or noisily movement.
Eg.
Học sinh thi vẽ tranh để cổ động ngày môi trường.
(The students draw pictures to launch propaganda for environment day.)
Eg.
Cổ vũ (to excite): using action or words to make someone fervent in doing something.
Eg.
Các fan hâm mộ đang cổ vũ cho đội nhà.
(The fans are cheering for the domestic team.)
Cổ xúy (advocate): encourage somebody by using delicate word, make him or her see the advantages or the need of the work that he/she is carry out.