Wrong: This lesson is considerable better than yesterday's.

Cute. A much overworked word. Use some expression that is more accurate; as, pretty, amusing, etc.

Decease, disease. Do not confuse decease and disease. The first means death, the second sickness. The deceased means a person who is dead.

Wrong: The diseased will be buried at four o'clock.
Wrong: The property of the diseased will be sold at auction.

Decease. Do not use decease as a verb in the sense of die.

Wrong: His father deceased last year.

Demand. Demand should not have a person as its object.

Wrong: He demanded John to pay.
Right: He demanded payment from John. He demanded that John pay.

Different. Use the preposition from after different, not than.

Don't. Do not use don't with a subject in the third person singular. See §64.