Ответ:

  1. It's very cold today. I should wear a jacket.
  2. He's got a toothache. He should take a painkiller.
  3. Mike feels very tired. He shouldn't stay up late.
  4. My friend is nervous about his exam. He shouldn't worry so much.
  5. His sister always loses her keys. She should keep them in her pocket.
  6. I broke my dad's new camera. I should tell him about it tonight.