Ought to (Ought + Infinitive)

The expression ought to (ought followed by an infinitive) is equivalent to should and should never be preceded by had:

think we had ought to leave soon

think we ought to leave soon = think we should leave soon

Negative sentences with this expression are formed by adding not between ought and to:

ought not to taunt the Hulk = should not taunt the Hulk

The contraction oughtn’t is acceptable, and sometimes to is omitted in negative sentences: “You oughtn’t taunt the Hulk.”