Learn English – Someone who forms their own opinion

Are you thinking of "prejudiced"?

One who doesn't take a stance on a subject can be characterized as impartial or indifferent

impartial (adj) - treating all rivals or disputants equally; fair and just:

indifferent (adj) - having no particular interest or sympathy; unconcerned*

One who can't make decisions on his own is certainly diffident:

adj - lacking confidence in one's own ability, worth, or fitness; timid; shy.

There are many options though. You should be more specific and maybe provide some context: apathetic, infirm, weak-willed, detached, aloof are all terms that spring to mind.

Medically speaking, a person who can't make his own decisions and constantly depends on others suffers from Dependent Personality Disorder.

New Oxford American Dictionary*